
who uses this word, mainly boys, mainly girls, tennagers, everybody amongst friends?

I would say it is fairly common, informally, up through the ages these days, but I believe young people have other forms of greetings. Maybe more used by males than females though.
It is short for "Tjänare", which literally means "servant"; cf. German "Servus".
Or what say you, @herrsilen?

I agree with @morbrorper. I said it to my neighbour just a few moments ago. My female colleagues also use it.
Other greetings I use: tja, halloj, hellu, tjabba, tjenare and hejsan (with various degrees of seriousness)
“Hej” is the standard greeting.

our Szervusz. bit more used by males
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