A self-tape is an audition that the actor films on their own and delivers electronically to their agent to be sent on to the casting director upon approval. Your agent will provide you with the sides, instructions and a deadline. It is then up to you to film, edit, and return it to them on time. 

These days, self-tapes are not only used for casting talent, but may even be utilised as the actual footage in a production. That is why capturing quality video is so important. It will give you an advantage over your competition.