When you don’t have proper bike chain lubricant to hand, you can use Vaseline instead. Most people already have it at home, so it’s convenient.
However, keep in mind that this isn’t what Vaseline was made for, so it won’t be as effective. Plus, it’s not as long-lasting, so you may have to reapply it after each ride.
Another drawback to Vaseline is that it’s hard to clean off, captures more debris, and is a fire hazard.