Learn about the three most basic types of values: booleans, strings, and numbers.
A boolean is a true or false value. These words are special and reserved. You can't name a variable 'true', because that word is already universal as a boolean (as is 'false').
A string is a set of characters that is set between either single (') or double (") quotation marks. This string can be named 'true', as long as it's between those quotation marks.
Numbers are pretty self-explanatory - a number is a value that consists only of digits, though it can also contain a decimal or a negative sign.