What is the difference between != and !== operators in JavaScript?

Yes, it's the same operator like ===, just for inequality:

!== - returns true if the two operands are not identical. This operator will not convert the operands types, and only returns false if they are the same type and value. —Wikibooks

I was about to post this W3Schools page, but funnily enough it didn't contain this operator!

At least, the !== is indeed the inverse of === which tests the equality of both type and value.

Yes, !== is the strict version of the != operator, and no type coercion is done if the operands are of different type:

0 != ''            // false, type coercion made
0 != '0'           // false
false != '0'       // false

0 !== ''           // true, no type coercion
0 !== '0'          // true
false !== '0'      // true