The B-side (or "flip-side") is a secondary recording that typically receives less attention; although some B-sides have been as successful as, or more so than, their A-sides.

What is B-side version?

It's a term for the song on the other side of a single that's usually not included in the album. It's become a more broad term now with vinyl singles not being as common and people will call any song not released on an album a B side.

Whats the difference between A-side and B-side?

The words now mean the types of song that are usually placed on each side of the record. The A-side is normally the featured song. This is the one that the record producer hopes will receive radio airplay and become a "hit". The B-side, or flipside, is a secondary song that often does not appear on the artist's LP.