When the director starts a scene and they are shooting, the only people talking are the principle actors with dialogue, and any secondary that interacts with them. Extras are directed to pantomime so as to not interfere with the sound being recording of the principles on set. There are exceptions.
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.