Record manufacturers produced different types of records to be played at different speeds. The RPM of a record refers to its number of revolutions per minute. Two main types of records, 78 and 33 RPM, vary in use, quality and popularity.
The first type of record to be mass produced was the 78 RPM record, which remained the most popular until after World War II. Then, companies like Columbia and RCA started manufacturing 33 RPM records.
78 RPM records have no grooves, meaning they can only hold one song. 33 RPM records can hold nearly an hour's worth of music, which is why they are also referred to as LPs (long playing).
33 RPM records are the largest in size, usually measuring 12 inches in diameter. 78 RPM records are usually 10 inches in diameter.
78 RPM records are made of thick and brittle shellac, which is highly breakable and causes edges to easily chip. 33 RPM records are made of sturdier vinyl.
Nowadays, it is difficult to find equipment that plays 78 RPM records, as manufacturers don't produce nearly as many 78 RPM record players as they do 33 RPM players.
Do not attempt to play 78 and 33 RPM records with the same type of stylus, as you can damage the records and stylus.