Can someone please explain to me what is the OFFSIDE rule in ⚽? ...

[EarlG]

9. If you know how offside works in hockey

then consider that soccer’s rule is similar, except in hockey the blue line is visible and in a fixed position, whereas in soccer the blue line is invisible and it moves up and down the field in sync with whichever member of the defending team is standing closest to his own goal (not including the goalkeeper).

There are other complications (such as the question of whether an offside player is considered part of the play or not, as in the OP’s example) the rules for which tend to get fiddled with over time. But I’ve found the easiest way to explain basic offside is the “moving blue line” analogy.

Of course, it’s not very useful if the person you’re explaining it to doesn’t know hockey either.