EP refers to Extended play. It is something between a single and a full CD (or LP); a little too short to be a full CD and a little too long to be a single.It usually has 3-5 tracks . LP refers Long Play; it is a vinyl record.
n this video, I discuss the difference between albums, ep’s, singles, and mixtapes, and how to decide which option is best for you. I have included a link to a great podcast by cdbaby which covers the topic more in depth. I hope the information helps you in your own songwriting journey.