An abstract Goal for pathing, can be anything from a specific block to just a Y coordinate.
A specific BlockPos goal
A composite of many goals, any one of which satisfies the composite.
Don't get into the block, but get directly adjacent to it.
Invert any goal.
Useful for automated combat (retreating specifically)
Dig a tunnel in a certain direction, but if you have to deviate from the path, go back to where you started
Useful if the goal is just to mine a block.
Useful for long-range goals that don't have a specific Y level.
Useful for mining (getting to diamond / iron level)