Ok, I've confused myself about the difference between the above.
As I understand it, a value bet is when you likely have the best hand e.g. the flop hits you and you want worse hands and draws to call to build the pot.
And a cbet is when the flop misses, but you may have the best hand.
So is a cbet a kind of bluff?
I have seen tuition videos where they say 'don't bluff at this level', then later say to fire in a cbet.
Would they differ in size?
Does it make any difference whether you are IP or OOP?
Where does a probe bet fit in?

a cbet can be a value bet. It simply means you continuation bet on the flop when you are the preflop raiser.

CBET = Continuation Bet.. it means you bet after beting preflop.

if you raised pre flop and its your turn to act on the flop and you bet out = cbet. If you get a caller and the turn is dealt, its checked to you and you bet out again - also a cbet. If you are the raiser pre everyone including you checks the flop then its checked to you and you bet the turn = delayed cbet! cbet stands for continuation bet - you are continuing the action with a bet.

A value bet is when you make a bet at any point because you think worse hands will call.

A continuation bet is any bet after you were the aggressor on the previous street.

A value bet is a bet where you believe you have the best hand AND you expect mostly worse hands will call.

Any given bet may be both, either or neither.

ok 4 people have written exactly the same thing (cbets can be for value or bluffs) so i'll try to address some of your other questions.

generally you want to keep your cbets the same size whether your bluffing or not. if you make it big when you're bluffing and smaller when you're value betting (or vice versa), it's going to be super easy to read you. the exception is when villains are so unobservant that they don't pay attention to your sizing.

if you're cbetting different sizes usually it's because of board texture. you can bet smaller on really dry flops like K72r or 882r because they will fold to the smaller bet most of the time because it's hard for them to have anything. on wetter boards people will float more widely if you make it cheap for them to do so by betting small.

i think by probe bet you mean a bet for information. this is a bad reason to bet in general. you should be betting for value or as a bluff. ok so if you cbet with A-hi on a K72r board and villain folds QJs then technically you've made a worse hand fold, but it's still a good thing to take down the pot now.

You shouldnt bluff "at this level" because people dont understand they are being bluffed and just call it down with bottom pair for instance.

You would cbet for value, as a bluff or to win the dead money int he middle.

Probe bets are "betting for information" and are bs. You should only bet for value, as a bluff or to collect dead money. When people call it a probe bet, they are most likely betting for value but the side effect of the bet is that they find out where they are e.g. villain reraises all in, we found out we were behind.

OK, really good answers, thanks.

One of my rules is not to bluff people who, as you say, don't realise they are being bluffed, another rule is not to assume they are bluffing, since they are often very easy to read (i.e. I haz a hand = big bet).

But what I do see a lot is that people assume I am betting and call when they have garbage.
And on certain sites I see very loose players bluffing hugely almost every hand (I reckon they've watched a bit too much poker on TV).

people generally don't call when they have nothing, which is why you cbet. if vsing someone who calls with everything don't cbet except for value. you see people play ******edly at low stakes wherever you go. you just gotta take notice and employ player dependent strategies.

People assume you are betting and call with garbage? Great! You want them to do that as you will make loads of money off them every time you have any kind of hand. keep up the good work!