Am i right in these defintions:

1) Betting for value is when you bet only if you have strength and you believe you can win
2) A bluff is when you believe you wouldn't win if the other person called you, but you bet because they have a decent probability of folding
3) A semi bluff is when you believe you wouldn't win, but have a small chance of drawing into a winning hand, and the other persons have a decent probability of folding

Right now I am ONLY doing #1. Are #2 and #3 profitable? I read somewhere that bluffing is -EV.

Also, you mostly bluff/semibluff only on flop and maybe turn right?