The card game poker is played by betting money on the value of a hand. A good player can win a lot of money simply by playing better than other players do, but they can also lose a lot of money if they make poor decisions or are caught bluffing.
In poker, the ante is the first amount of money put into the pot before any action starts. Then each player has the option to raise, call or fold. A raise is to add more money into the pot than the previous person. To say you want to raise, you have to raise your hands over the cards to show that you are raising and give other players time to react.
If you have a strong hand and think your opponent is likely to call a bet, then raise the amount of money you bet. This will force weaker hands out and improve your chances of winning the pot.
Generally speaking, the earlier in the hand you act, the tighter your range should be. For example, in EP you should only play your best hands pre-flop. In MP, you can open up a little bit but you should still play mostly top pair hands and high suited cards.