RPM stands for revolutions per minute, as in how many times the platter will spin completely in a minute. Vinyl records are produced to be played at one of three speeds: 33 1/3 RPM, 45 RPM, and 78 RPM. You will almost never deal with 78 RPM records, so don’t worry about that. Most full-size 12-inch records will be 33 1/3 RPM, though some — mainly EPs and maxi-singles — will be at 45 RPM. The vast majority of 7-inch singles will be 45 RPM, and 10-inch records…well, that’s more of a wild card. The RPM of a record will be printed somewhere on the record label, and all you need to do is switch your turntable from 33 1/3 to 45 mode.