It's a very complicated issue buddy but I'll try to help you with my little understanding of the game. (I play poker for about a month or so).
In tournaments, when players are with deep stack, they tend to raise very strong, without any good hand for practical and tactical reasons:
1) The player deep stack got nothing to lose. It is not likely someone would re-raise a raise of five big blinds or more. And if they do re-raise, they are entering into a delicate situation, because the guy with deep stack is not thinking about fold.
2) If nobody calls ou re-raise the deep stack collects the dead money and the blinds, which is not bad for him.
3) there are players low stack in the game, praying for a situation where they go all in with less than 10 big blinds of stack. The player who has deep stack is not worried about short stacks, because no matter what hand they had, the deep stack is ahead in any dispute. For instance, a guy with 220 BB of stack, re-raises in utg position to 6 times big blinds. The guy in the Cut off calls it with his entire stack. Now the hands, the deep stack in utg has 72 off and the guy in the cut off has pocket aces, AA. But it doesn't really matter for the guy who has 220 big blinds as stack, because his adversary might even lose with pocket aces over 72 off suit! It's possible and it happens more often than players use to believe.
Anyway the deep stack player is betting in a huge range of hands, because it's profitable for him in this situation to attack and be extreme agressive.
Now the range of hands. When you are playing you should always ask yourself: "What kindda hands my opponents have to play and do things as they do?". For example, in a tournament were blinds are 10/20, the utg begins limping, the utg 1 limping, utg 2 limping, utg 3 folds, hijack folds, cut off raises to 3 big blinds, the dealer re-raises to 5 big blinds. The small blind position folds, the big blind position calls, the utg folds, and utg 2 calls, and the cut off calls as well.
Which hands made the players bet those particular ammounts? Well, the utg got very weak hands, because he limps and folds to re-raise. The utg 2 might have something because he called a strong raise. Which means, the utg 2 maybe is involved in a good range of hands so as the cut off and the button position in the example above.
Online players do not bluff too much, as it seems. They are betting in hands with
equity, with possibility of winning and there are a few of them who bet over any possible hand.
Try to think the range of hands by what yourself would do with x starting hand, in x position. If you got, for example, pocket kings, KK, in the button, what would you do? Would you fold? Well, you might sometimes, but it's very hard to fold a hand as KK. Would you limp with KK pre flop? Maybe not, because it's not good, in general, to make slow games with a hand that could lose to any Ace x (Ax = A2, A3, A4, A5, A9, A10, etc)
So the right move for a player in the button, holding KK pre flop is to raise between 2 and 5 big blinds, in a clear attempt to cast out player who might have a range of hands as A6, A4, A3, etc. If you just limp trying to make slow with pair of KK pre flop, you might allow another player to limp with A2 and get a free Ace in the flop. Raise to "hold" your opponents, to make them fold pre flop and get called only by strong hands.
If you made a big raise and got called, you may expect a strong hand, generally speaking. See what you do, and why you do with the starting hands you get, then start observing and analyzing other's move to catch their range of hands and play more safe.