They're referring to C types on a particular architecture. In C, long
is a type of variable. Its size varies as a function of the compiler, but in this case it's a 32-bit value. Words are processor words, which are typically 32 bits in modern parlance. However, Warcraft 2 was written a long time ago and runs on 16-bit machines. As Sean pointed out in a comment, words are 16 bits in this context.
To answer the question in the comment:
16 longs = 16 * 32 bits = 512 bits = 64 bytes.
110 words = 110 * 16 bits = 1760 bits = 220 bytes.