The era of the 78 rpm (revolutions per minute) disc started in the late 1800s. These discs were heavy and fragile and the quality wasn't always ideal. They were often one song per side. In order to purchase several 78's together in a collection, you'd buy an "album" (which looks a bit like a photo album) which would house the entire collection together. The term "album" continues to this day, referring to a collection of records.
Liner Notes on these collections were usually printed on the inside of the "album" and consisted of an essay or basic information about the recordings. They rarely contained performance information, no artist or musician lists, no information about where or when the recordings were made. Very often, these Liner Notes were simply advertisements for other recordings available by this artist or the recording company.
Eventually, more discs would start being manufactured. The 78 rpm was king until the mid-50's. The 33-1/3 speed would eventually become more common for collecting an entire "album" on one, double-sided disc, commonly referred to as an "LP" (Long Player). This would be the preferred format for "albums" until the late 1980's.
It was on the 33-1/3 speed "album" that the term Liner Notes even came into existence. Inside the "album" cardboard cover, the vinyl record was usually protected in a thin paper sleeve. This sleeve (the Liner) usually had the information on it (the Notes).
These notes varied from simply being advertisement to containing the lyrics (this was common from the late '60's on). Sometimes they contained basic recording information or messages from and biographies of the artist(s).
Single recordings would change from the 78 rpm to the 45 rpm speed, with one song per side. The 45 rpm single would be standard-bearer for teenagers all over America from the 60's through the 80's. 45 rpm singles rarely had any information on them. Sometimes several singles would be released on a 33-1/3 album, called an "EP" or Extended Play.
When CD's first started coming out in the mid-'80's, they were usually exact copies of the original "album." It was only when the record companies figured out that we (the consumers) were going to re-buy everything all over again that they realized they could maximize their profits by adding new information and extras.
That's when Liner Notes started to really have all the information that we love.
With the advent of digital music, Liner Notes are again fading away and terms like "album", "LP" and "EP" are still used today in the music industry.