== is used to check for relative equality, whereas === is used to check for strict equality.
In other words, the string '2' will evalutae to true when compared to the integer data type for 2 for equality.
=== will check to see if the contents AND data type are the same, so since a string and an integer aren't the same, it would evaluate to false.
TLDR:
'2' == 2 will evaluate to True, since the contents are the same
'2' === 2 will evaluate to False, since the data types are different.