Cyrillic is one of the first Slavic alphabets (another alphabet is called the Glagolitic). In the year 863 Prince Rostislav invited from Byzantium two brothers, Christian preachers Cyril and Methodius, who were supposed to lead worship. Naturally, in order to understand them, they had to preach in the Slavonic language. And that the Slavs could read the Bible, written in Greek, Cyril and Methodius created the Slavic alphabet, which was called "Cyrillic". Later from this alphabet were born and others, including Russian and Ukrainian.
The Glagolitic alphabet was created by Cyril and Methodius. This alphabet is different from the Cyrillic form of letters. The Glagolitic alphabet was spread in the X-XI centuries in Bulgaria and Moravia. And in Croatia it lasted until the end of the XVIII century.