It is amazing how differently you think about the game of poker when you first stumble upon the game. In the beginning, it is not unusual for you to want to play every hand. You will normally be playing for free, or if you are playing for real money it is not often for high stakes.
You want action and being involved in every hand is action personified. You may even find experienced players who still play the same way, you cannot win the pot if you are not in the pot, is an all to common excuse used by these types of players; bad players.
As your game progresses you start to understand how important it is to have the best hand at showdown. This seems so blatantly obvious but you would be surprised how many players lose three streets of value with [Qx] [Tx] on a ten high board versus [Ax] [Tx]. It is a question of: dominate or be dominated? And players improve when they realise this simple truth, and start folding.
A big fold can easily be described as folding a non-nut hand, in a spot where there are very few probabilities that you can be beaten, but the sequence of action and the table image of your opponent creates the belief that you are very likely beaten. In these instances the most important factor in your decision should be the size of your chip stack.
If you are deep stacked or have a great advantage over your opponents then you can make more calls, but if your chip stack is at the more vulnerable end of the barometer, then the big folds become all the more important in the hope that better situation will emerge at a later time in the competition.