It supports binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16).
Divide the decimal number by 16 repeatedly and record the remainders. Read the remainders from bottom to top. For example, 255 in decimal is FF in hexadecimal.
Hexadecimal is used in programming, colour codes, memory addresses, and encoding because it compactly represents binary data (4 bits per hex digit).
10 in decimal is 1010 in binary.
255 in decimal is FF in hexadecimal.
Computers use binary because electronic circuits have two stable states: on (1) and off (0). Binary maps directly to these physical states.
Octal (base 8) is used in Unix/Linux file permissions (e.g. chmod 755) and in some older computing contexts. Each octal digit represents 3 binary bits.