Emperor Charlemagne apparently tried to learn how to read and write, but with poor success. Probably part of his difficulty was that he had to spend a bunch of time conquering countries, part of the difficulty was that he started learning later in life, but probably part of the problem was that it was very difficult. There were a bunch of different variations on Latin script that were used, the letters were all crammed together, you couldn’t always tell where word boundaries were, it was even harder to tell where sentence boundaries were, and even abbreviations were different in different “dialects” of the script.
Being the emperor, Charlemagne could do something about it. He called Alcuin, a hotshot scholar, teacher, and cleric of the day to come to his court and um, do something about it. Alcuin looked at the different dialects of Latin script that were in use, and came up with a standardized version of the script.
They also instituted looser spacing: letters were to have one space between them, words two spaces, and sentences three. Obviously, these spaces were smaller than the space character we use now.
(Alcuin’s team popularized spaces between words, but they did not invent it. The Lycians sometimes used spaces between words, but the Europeans forgot about the idea for a millenium. Irish monks apparently came up with the idea independently, about a century before the Carolingian reforms, and this time it might have been done out of necessity. While the Italian or French monks’ native language was a direct descendant of Latin, the Irish monks’ native language (Gaelic) was a much more distant cousin and thus much harder to for them to read. Breaking the words up with spaces was probably a coping mechanism for the Gaelic monks, and probably helped Charlemagne a bit.)
In addition to spaces to divide letters, words, and sentences, the Carolingian reforms encouraged even more visual cues for sentence beginnings and endings. Sentences were to start with a capital letter and punctuation was to show where the reader was supposed to stop or pause. This was the first time that capital letters (majuscule) and lower case (minuscule) were mixed together. Before, they were just thought of as essentially different fonts. There are only a handful of other writing systems that have both upper and lower cases.
With Charlemagne’s backing, Alcuin’s own scholarly reputation, and a hefty dose of money (in the form of hiring lots of scribes to make lots of copies of lots and lots of manuscripts written with Alcuin’s specifications), Alcuin was able to promote the script effectively and succeed in getting people to standardize on one script: the so-called “Carolingian minuscule”. People also started spacing letters, words, and sentences, and using punctuation.
In my opinion, this was a very big deal.