Once, I was playing ADR when a Scout came. He/she was selling a few maps so I bought them. They didn't seem to do anything and I'm afraid I wasted some resources. What do maps actually do?
You didn't waste resources; anything you spent on maps still earns you the benefit. You may simply have not progressed far enough yet to see the results.
Non-spoiler answer: keep playing. You'll soon reach a point where you can see the results of your purchase.
Further answer, with spoilers:
Eventually you will unlock a new location called 'A Dusty Path'. This will let you journey out into the world and explore your surroundings. When you do, you'll see that some of the areas have already been mapped out - this is due to your purchase from the scout.
Full answer, with more spoilers:
To unlock 'A Dusty Path' you need to obtain the
compass, usually through trade. You'll need to set some
trapsand earn enough
scalesto trade for it. Once you have the compass you will also need to build a
smokehouse, so you can cure meat to travel.