Parkour is a minigame in various different servers. This minigame involves jumping from block to block, avoiding obstacles such as lava. Parkour sometimes uses Potions to help aid the jumps and speed, like Potion of Leaping and Potion of Swiftness. Most parkour maps have checkpoints, which keeps the Player from starting all over again.
Regular Parkour only involves the Player jumping from block to block. Sometimes obstacles are involved. The maximum blocks the Player can jump without changing the Y-axis is 4 blocks. If the Y-axis is moved up by one, the Player can only jump 3 blocks.
Ladder Parkour is a bit harder than Regular Parkour. This involves jumping to ladders either by climbing ladders or standing on ladders. Often, Players sneaks when on ladders to prepare for the next jump. Ladders are way thinner than a full block, so it will be harder to step on.