Bela-

>I am not a native english speaker, and I saw several times, that the usual name for an object in examples is FOO. Does it have any meaning? Is it a short version something?

Foo and bar come from FUBAR. An acronym meaning Fuc*ed Up Beyond All Repair. I think it's a military term. That's evolved to a convention of programmers using Foo and Bar for names of code elements in examples. It's a flag that the name has nothing to do with the concept that's being communicated. Or it's a stand-in.

I hope this helps.