It's British/Australian usage, mainly. Men say "cheers" a lot more than women. If a woman says it, it comes across as a bit masculine. I almost never say "cheers".

When non-native speakers use it, it's a sign that they lived in the UK for a while, or spend a lot of times with Brits / Australians / Kiwis.

It's also informal, not "RP" speech. Prince Charles wouldn't say it (but William and Harry might). Number one users of "cheers" are pub landlords, black cab drivers etc. Blue collar workers.

I.e. highly educated / posh people don't use it.
They'd say "much obliged" or "I really appreciate it, thanks a lot" or something like that.

Usually the expression is "Cheers mate!" in speech.

You use it to PEERS (friends, co-workers at the same level), absolutely not to your boss, elderly people you respect etc. Usually between men.