A numeral system is a way to express numbers using a consistent set of symbols and rules. The most common system is the decimal system, which uses ten digits (0-9) to represent all numbers. Other numeral systems include the binary system, which uses only two digits (0 and 1), and the hexadecimal system, which uses sixteen symbols (0-9 and A-F). Each system has its own applications, especially in computing and mathematics. Numeral systems can be classified as positional or non-positional. In a positional system, the position of a digit affects its value, as seen in the decimal system where the number 345 means 3 hundreds, 4 tens, and 5 units. Non-positional systems, like Roman numerals, do not use position to determine value, making them less efficient for calculations. Understanding these systems is essential for various fields, including computer science and engineering.