An infinite series is a sum of an infinite sequence of numbers. It can be thought of as adding up an endless list of terms, like 1 + 1/2 + 1/4 + 1/8 + ... This series gets closer and closer to a specific value, known as the limit, even though it never actually reaches it. Mathematicians study infinite series to understand their behavior and convergence. A series converges if the sum approaches a finite number as more terms are added. For example, the series mentioned earlier converges to 2. Understanding infinite series is essential in fields like calculus and physics.