The equals sign assigns a value to a variable. The variable must be on the left side and
must be a single word (no spaces); however, it can be as long as you like and can contain
numbers and the underscore character (_). Also, characters can be upper- and lowercase.
Those are the rules for naming variables; however, there are also conventions. The differ-
ence is that if you break the rules, Python will complain, whereas if you break the conven-
tions, other programmers may snort derisively and raise their eyebrows.