okay, i own nothing friends related but i wanna buy the full series. is there like different types that have different bonus/interviews/bloopers in them? if so, which is the best to buy?
Yup, there is. If you're in the US, and it's the DVD version you're after, you will want to get this set. Or you could always buy the individual seasons (slowly build up your collection). Both of these have the extended episodes, plus all the extra features that were ever added to any DVD sets (gag reels, etc).
If you're outside the US, the equivalent to that complete box set is this one.
The blu-ray set, while obviously of higher quality, does not have the extended episodes. The episodes on this set are the original aired/broadcasted episodes -- the versions you'll see in syndication on TV. They do, however, have all the same extra features the DVD sets have, plus a disc of new features none of the DVD sets have (new unseen gag reel, 3 new documentaries about the show, some old cast interviews, etc).
US blu-ray | UK/Europe blu-ray
For some reason, the UK version of the DVD box set is a whole lot cheaper than the US one ($64/£40, while the US version is $139/£87), even though, content wise, they are the exact same. So if you are in the US, and have a multi-region DVD player, order the UK set.
The UK blu-ray set (which is also slightly cheaper) is region free, so you can order that and it will play on any BD player from any region.