Full Idea
A sentence's truth conditions comprise an exhaustive list of the situations in which that sentence would be true.
Gist of Idea
A sentence's truth conditions are all the situations where it would be true
Source
Tim Button (The Limits of Reason [2013], 03.4)
Book Reference
Button,Tim: 'The Limits of Realism' [OUP 2013], p.23
A Reaction
So to know its meaning you must know those conditions? Compare 'my cat is licking my finger' with 'dramatic events are happening in Ethiopia'. It should take an awful long time to grasp the second sentence.