HEX2BIN is a Google Sheets function that converts a signed hexadecimal number into its equivalent binary representation. A signed hexadecimal number is a number that can be positive or negative, represented in the base-16 number system. The binary representation is a sequence of 0s and 1s that can be interpreted as machine language by the computer.

The function takes two arguments: the signed hexadecimal number and the number of significant digits (optional). The significant digits parameter determines the number of bits used to represent the binary number. If the significant digits parameter is not specified, the function uses the minimum number of bits required to represent the number.

For example, if we have the signed hexadecimal number "FF" and we want to convert it to binary with eight significant digits, we would use the function HEX2BIN("FF", 8). The result would be "11111111" which represents the binary equivalent of the signed hexadecimal number "FF".