The sequence "1010101" is a binary number, which is a system that uses only two digits: 0 and 1. In the binary system, each digit represents a power of 2, starting from the rightmost digit. For "1010101," this translates to the decimal value of 85 when calculated. Binary numbers are fundamental in computer science and digital electronics, as they are used to represent data and instructions in computers. Each binary digit, or bit, can be thought of as a switch that is either off (0) or on (1), allowing complex information to be processed and stored efficiently.