Quote Originally Posted by Thunder
Eg: you hold 10A and the board shows 7 10 10 K K
Or you hold 78 and the board shows 782Q8.

Or any such combo where your top set caneb outgunned.
You don't have a set in either of these hands. A set is where you have a pocket pair and hit the board. Otherwise it's called trips. To answer your question just think about what hands beat yours and think of how likely it is for your opponent to have that hand. In your first example, any king beats you. In your second example you're only beat by Q8 and QQ. The difference is huge.