re: Poker & The Reasons for Raising
Check raising is usually reserved for situations like :
When you call a preflop raise OOP, and you flop something like 2-pair or a set on a wet board. Even OESD with FD is a good spot to C/R flop. Since we are usually checking to the raiser almost always (if we think he will c-bet), it is a much stronger line than say donk-betting into the raiser. It also allows us to get more money into the pot when we smash the flop.
Also check-raise can be used as a stone cold bluff if we think villain has air. A good read is required for this little play.
Raising in general:
Let's say you open and get one caller from the BB. The flop comes out, draw heavy, and you hit top pair. Villain decides to donk bet the minimum into you. Punish him for this. Raise him full pot. People frequently do this stupid stuff with hands like gutter balls, bottom pair, weak PPs, and all sorts of garbage. Villain will rarely take this line with a strong hand. It is basically a defensive bet to try and slow you down, or even get you to fold. PUNISH villains for this tom-foolery with a nice big raise.
Raising on the river:
Either a bluff (not advised without excellent read), or flat out because you think you have the best hand (for value).
In poker, aggression alone can win many pots. Raising and taking strong lines will help you gain control of the hand, and put your opponent on the defensive. Put pressure on your opponents whenever you think they are weak, or chasing. Make them make the tough decisions. Don't allow them to gain the upper hand if at all possible and prudent.
However, don't get carried away and spew. Semi bluffs, and made hands. Semi bluff with draws to NUT straight, FDs, combo draws, etc.