It is played on the same board as checkers, a simpler game, which has been solved and is realistically possible for humans to play perfectly. This means that the base of 8x8 for a board is fit for solvable games, granted that the implications of this are small. chess is not really that much more complex than checkers though - it has relatively few rules as well.
There are tons of patterns in chess. For instance, the pieces move in all possible ways that the 8 directions allow for in the 8 squares of possible movement. (Aside from pawns, which will be furthered explored later.) Disregarding everything but square alignment, Bishops move diagonally, Rooks move horizontally/vertically, Queens do both of those movements, and each of them can go any number of spaces if the path isn't blocked. Kings movements are the same as a queens, but only in a single space. Knights also move in a diagonal path - however, it is a more complex one than a bishop's path apparently. Rather than a slope of 1, it's a slope of 1/2 or 2. They are interesting because this diagonal doesn't follow a direct path - wher bishops movements can be seen as linear based on the corners of the squares, knight movements are wacky. Apparently.Consider the diagram to the right. Red is rook movements, blue is bishop movements, and green is knight movements. Though the knight supposedly follows a "weird" path, it is actually just the next division of possible movement.
The most logical way that you can see a knights path is a "Z" shape, like those terribly obnoxious tetris pieces, as plotting a line from the center of the original and terminal square of their movements would follow this path. However, this was apparently not intuitive enough and was not chosen as their "true" movement. This is the case because all other pieces do have a "true" movement demonstrate this restriction. How? Because you're not allowed to pass through your pieces or land on the same square as your pieces.
Knights still follow the rule that they can't land on the same square, but they CAN jump over pieces. If the Z shaped motion path had been chosen as their "true" path, then it would make sense that their path could be blocked and they wouldn't be able to jump pieces. However, if you choose to interpret their movements as an L shape instead of a diagonal, suddenly the path might not be obstructed! The problem is that the L shaped movement could follow either path - as in, it could go in an L or an ˥. Both paths make sense, but one might not be blocked while the other is. In that case, they could make the movement rules more tedious and say "You assume the path is blocked if one is blocked" or "You assume the path is unblocked if one is blocked." But then you have to go into this convoluted L shaped path explanation. Nah, that's a pain.
But what about the logical Z shaped path? After all, that's the shape you get when you plot the shortest line between the first and final squares of its movement. Nope, that path is too ridiculous to explain too. Amusingly enough, the Z shaped path would be following the above rule that "You assume the path is blocked if one is blocked." Anyway, that makes the Knights movements totally ridiculous. If they don't follow a "true," blockable path then for all we know their path could actually be to move up 5, over 6, down 4, and over 4 in the other direction, because why not? The effect is the same. Oh - but the method isn't!
You see, that motion path could involve moving off the board before returning to it, and that is universally disallowed in chess. No, the only real possibilities for a Knight's movement are the L or Z shaped paths because those are the shortest paths (accounting for cardinal movements) and thus the most obvious ones to prevent movement off the board. Yes indeed, it must be one of those three. But no, no it isn't any one of them particularly. Knights simply magic their way from one square to the next. They are wily that way.
And so, they are the Queen's worse enemy - no piece can threaten a Queen from safety but the Knight! You mad, queenie? They also pose an unconventional threat to the King - No other piece can smother the King in a mess of his own pieces and nothing else. The Knight has but one enemy he can face-off in a fair fight, and that is another Knight. What a poet the Knight must be. Anyways, onward to pawns.
Pawns have, unequivocally, the most rules associated with them of any piece.
They can move two spaces forward, but only on the first turn!
They can only move forward, unless they're attacking!
Which they can't do forward, by the way. Only diagonally. Pawns must attack diagonally. That includes when they move two spaces forward, bub.
Oh - and if they decide to move two spaces forward to rush by another pawn and avoid being attacked? En passant! The empty space behind the moved pawn is equally vulnerable, as if it had only moved a single space.
But it's only vulnerable to another pawn! (that's necessary for avoiding unfairness in endgames, mind you).
If they cross the board, they go from a lowly peasant to the royal majesty herself, a Queen! Or a Rook! Or a Bishop! Or a Knight, even. Do you really want a Queen when you can have a Knight? Just saying.
"Why would you ever do that?" you might be wondering. And the answer, it is so obvious. Because Knights are way cooler than Queens, that's why. Have you ever seen someone demonstrate a fork with a piece other than a knight? Didn't think so, Knights rock.
Point being Pawns are weird little fellows that break from the above destriptions of movement. While all the other pieces follow mathematical slopes - 0 or ∞, the Rook, 1 or -1, the Bishop, 1/2 or 2/1, the Knight. And there's the movement of the prior 2 for both the King and Queen. In all spaces, and a single space. But the pawn is riddled with so many rules that are just "arbitrary" by comparison. And that is why the pawn is the "soul" of Chess. Its movements are somewhat unconventional.
Another interesting rule - you can not castle through check. "Why is that interesting?" you might be asking.
Well stop asking questions and let Flame Prince Finn explain.
Being impatient won't get you anywhere. Calm down.
The King always moves a single square, yes. Except when castling. This means that there is one square that is left in a weird limbo of "Is it okay for him to castle if I have a piece threatening it? He couldn't move his King there in two moves one space at a time, but a single move, is it allowed? Technically I'm not threatening the King on any turn." The answer isn't obvious, but no, you are not allowed to castle through a threatened square - because just as with every other piece, the Kings path follows a true movement. Where a Bishops true path cannot be obstructed be one of your own pieces, a King's castling path cannot be obstructed by an opponents threat. Yes, every piece except the Knight has a fixed path of motion that can be obstructed in some way or other.
So it all comes back around to how amazing Knights are. Knights break all the rules. And by "all the rules" I mean "every rule that the other pieces logically seem to follow." Knights don't let logic stand in their way.
Be a Knight. You might get laid.