Black’s queen on a7 is checking along the long diagonal, a7-b6-c5-d4-e3-f2-g1, and White is not in serious trouble, because she cannot come through anything. One knight move, 1.Ne3, drops a piece into the middle of her line and the check is over.
7 
2 
g That is the rule in Article 3.5, and it covers three of the six pieces: the queen, the rook and the bishop may not move over any intervening piece. They stop at the first one, and capture it only if it is an enemy.
The pawn is stopped by anything
Pawns get blocked hardest of all, because they capture diagonally and cannot take what stands directly in front of them. A white pawn on e4 with a black pawn on e5 is stuck there permanently, and so is the black one. Fix a few pairs like that and you have a closed position where knights are worth more than bishops.
The knight, and only the knight
Article 3.6 defines where a knight lands and says nothing whatsoever about the squares in between, because there is nothing to say. It jumps. On the very first move of the game, when every other piece is buried behind pawns, the knights can already go to a3, c3, f3 or h3.
There is one more crossing in the Laws, and it is not really a jump: in castling, the rook and the king pass each other. Kingside the rook lands on f1 while the king lands on g1, having each crossed where the other one ended up. That is a single special move, though, not a power the rook keeps.
Why this makes tactics work
Every pin, every skewer, every discovered attack in chess exists because pieces get in each other’s way.
A pin works because your bishop cannot legally step off the line and let your king be taken. A discovered attack works because a piece that was in the way moves and something big wakes up behind it. And when you are in check, the fact that the checking line can be filled is one of the three ways out, which is why a knight check is so much nastier than a queen check: there is no line to fill.
Learn the pin first. Half of all tactics at club level start with a piece that cannot move.