SQL Query Joins

Question

SELECT * FROM a JOIN b ON table_a.id = b.id WHERE table_a.status ='success'

 

SELECT * FROM table_a, b WHERE table_a.id = b.id AND table_a.status ='success'

 

Why is the second format used and not the first one?? Is it due to performance reasons?

If yes then how or why. Please explain in detail.