ON is used when referencing joins and where is used for filtering data. Explicit join is using ON and implicit join is used with WHERE.
Performance-wise both are identical but for readability is better to use ON to separate out when you are using WHERE to joining tables or filtering a table.
SQL example, all three queries produce the same result:
SELECT * FROM facebook JOIN linkedin ON facebook.name = linkedin.name
SELECT * FROM facebook JOIN linkedin WHERE facebook.name = linkedin.name
SELECT * FROM facebook, linkedin WHERE facebook.name = linkedin.name