This is called the \"Cozio Variation.\" It's currently in vogue, being used by dynamic players who want to spice things up a bit when playing as Black. The white player needs to be ready for a large number of sub-variants when he places the bishop on b5 and chooses the Ruy Lopez (the best chess opening).
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1b5 