Theorem 1: If two lines intersect, then exactly one plane contains both lines.
Theorem 2: If a point lies outside a line, then exactly one plane contains both the line and the point.
Postulate 1: A plane contains at least three noncollinear points.
Postulate 2: If two planes intersect, then their intersection is a line.
Postulate 3: If two points lie in one plane, then the line joining them lies in that plane.
If you don't know the difference between theorem and postulate, a theorem tells the truth and can be proven, while postulate is only assumed to be true without any proofs.