A geometric progression (GP) is a sequence of numbers where each term after the first is found by multiplying the previous term by a fixed, non-zero number called the common ratio. For example, in the sequence 2, 6, 18, 54, each term is obtained by multiplying the previous term by 3. Geometric progressions are commonly used in various fields, including finance, physics, and computer science. They help model exponential growth or decay, such as population growth or radioactive decay. The formula for the nth term of a GP is given by a * r^(n-1), where a is the first term and r is the common ratio.