What's the difference between keywords 'test' and 'it'

In a few different testing frameworks I've seen some people using keyword 'test' and some using 'it' when creating tests, while both seem to be valid keywords and don't seem to change the test at all.

So what are the differences and where should I use them?

Tried googling this but you can imagine how Google might not understand 'test' and 'it' as coding keywords so the results had no info on this issue.