The sequence "111100111" is a binary number, which is a system of representing values using only two symbols: 0 and 1. In this case, the number consists of five 1s followed by four 0s and then two more 1s. Binary numbers are commonly used in computing and digital electronics because they align with the on/off states of electronic switches. When converted to decimal, "111100111" equals 455. This conversion is done by calculating the sum of powers of 2 for each digit, where each position represents a power of 2, starting from the rightmost digit. Understanding binary is essential for fields like computer science and information technology.