Linux – less is more? Is more less? I’m so confused

lesslinuxposixterminalunix

When I first heard their names, I got really confused when I tried to guess what these tools might do, I thought I'd misheard something.

What's the difference between more and less, i.e. why should I choose one over the other?
They both seem to do the same thing…

Also, why are they named like that in the first place?

more is a basic pager, which allows you to scroll downwards, one page at a time. Only downwards.
less is also a pager, but has addition functionality to scroll upwards and downwards through the input, in addition to several other extensions.
So, yes. less is more, and more is less. Another common idiom (according to the wiki entry) is "less is more, more or less." The name comes from the fact that the author (Mark Nudelman) essentially wanted a program that was "backwards more" -- The opposite of more, is less.