In general binary means it can only take two values, so you could encode the vector using -1 and +1. However, in a computer context, we use binary to talk bits

In general binary means it can only take two values, so you could encode the vector using -1 and +1. However, in a computer context, we use binary to talk bits (1 and 0). The Wikipedia defines binary numbers as >A binary number is a number expressed in the base-2 numeral system or binary numeral system, a method of mathematical expression which uses only two symbols: typically "0" (zero) and "1" (one). So I don't think saying "typically" is an error.