First, there is no technical difference between the terms background (abbreviated as BG) or extra. They both mean the same thing — performers who don’t have lines, who are seen in the background of a shot, but who play a vital role in making a shot appear realistic.
Can I wear jeans to an audition?
You don’t need to dress like you’re going in for a corporate interview here. Your clothes shouldn’t be a wrinkled mess, but you also shouldn’t be wearing business attire to an audition. A good pair of jeans can go a long way, and it’s worth investing in a pair for auditions alone.