The key is in the word mate 'supplements'.
If you're on a good diet then you'll see the benefits, otherwise they're a waste of time.
Creatine is probably the best researched of all supps, it's shown to improve strength marginally and help with recovery. It's naturally available in food but you'd have to eat a **** load of it to get what you'd get from one scoop, I think it was like 3lbs of Tuna or something ridiculous. I use hydrochloride rather than monohydrate due to less bloating, or no bloating at all in fact, despite the fact it tastes like ****!
BCAA - branch chain amino acids, without these things I have a lot more muscle soreness post-workout. There's a lot more reasons that they're good for you but that's why I use them personally.
Protein powder is just a supplement mate, I use it in my daily diet as my 'something sweet' as I have a sweet tooth and I obviously can't eat chocolate and sweets etc. They say aim for 1g of protein per lb of bodyweight, which puts me dead on 200g of protein, which I can usually achieve quite easily with foods, but with the supps I'll take it to around 260g. Personally that's where my optimum seems to be for best gains, no logic to it other than that.