=
is the assignment operator. It sets a variable (the left-hand side) to a value (the right-hand side). The result is the value on the right-hand side.
==
is the comparison operator. It will only return true
if both values are equivalent after coercing their types to the same type.
===
is a more strict comparison operator often called the identity operator. It will only return true
if both the type and value of the operands are the same.
I would check out CodeCademy for a quick intro to JavaScript.
If you prefer to read more, MDN is a great intro as well.
For those concerned about the source of the term “identity operator” jbabey pointed out that JavaScript: The Definitive Guide seems to mention it.