What is the difference of lp and ep records?

There isn't a simple answer to the question because the answer is different for different time periods and formats. First, definitions: LP= Long Playing; EP= Extended Play. When using the term "lp" you are generally referring to the standard 12" record with 4 or 5 (more or less) songs on each side.

Back in the late 1940s and early 1950s, the first "EPs" were produced. These looked like a standard 7" 45rpm single with the big hole in the center. However, the EP was produced to have MORE than 1 song per side and still be played at 45rpm speed. Most of these EPs have 2 songs per side. Elvis Presley and Frank Sinatra released a lot of their songs on EP, and The Beatles released 1 or 2 in the US...Very Collectible!!! Today, the EP could stand for 12" singles that have extended remixes as well on the record, especially if they are meant to be played at 45rpm.