Premium and Non-Premium Hands
A premium hand is a hand that is fully expected to be the best hand before the flop. For instance, if you have two Aces, two Queens, an Ace, and a Queen or two high pairs, such as a pair of Kings or Queens, then this is considered a premium hand. These are more likely to turn into winning hands after the flop. Be careful how you play these hands; never fold a premium hand.
When to Play Non-Premium Hands
Normal hands are considered non-premium hands, and just because you get a non-premium hand does not mean you have to fold. You can play when you want to bluff, but you should be careful not to bluff often and become readable. Also, non-premium hands like small pairs can turn into the best hands of the entire round after the flop; this all depends upon the progression of the game.
Folding or Playing
Many people recommend that in Texas Hold'em and similar types of online poker, you should play fewer hands, especially if they are non-premium. This can be true because it minimizes the amount of money you lose, but there are also benefits to playing, in many cases. After all, sitting out hand after hand is no way to make money. It is wise to learn bluffing techniques and how to read a player tells in order to get the most out of the game.
Knowing when to play non-premium hands is one of the things that come with experience. As you continue to play the game the chances of winning is big and gain that experience, you will instinctively know when it is a good idea to play your non-premium hands.