A set can be category as an infinite or finite set, depending upon the number of elements it has. A finite set has a finite number of elements while an infinite set has an infinite number of elements.
For illustration, set P underneath has ten elements and is hence a finite set. Set S, on the other hand, is an infinite set because it has an infinite number of elements.
P = {2, 4, 6...20}
S = {1, 3, 5...}