Winning poker players use different playing styles. It’s one of the beauties of poker that players with very different styles can be winning.
For beginning poker players, the tight aggressive style is recommended. 
Aggression has to do with how often you bet and raise in the hands that you play. Calling is not considered an aggressive action.
Each time you call another player’s bet or raise, you get a point for passivity. When you bet or raise, you gather aggression points.
Even if long time winners use different playing styles, the tight aggressive style is the safe point of departure when you start out in poker.
The reasons are simple. By choosing your starting hands selectively, you will enter the pots with decent holdings. You will often be in a dominating position against your opponents who play more hands and therefore have a worse hand on average.