There are seven notes of music and two different systems to name the music notes: A B C D E F G and DO RE MI FA SOL LA SI.
You can learn to read music notes online for free with both DO RE MI FA SOL LA SI and A B C D E F G.
The syllabic musical notation: DO RE MI FA SOL LA SI
The origin of the syllabic notation is due to the Italian monk Guido d’Arezzo (XIth century) who used the first syllables of a Latin hymn to name the music notes:
DO (or UT) – RE – MI – FA – SOL – LA – SI
The alphabetical musical notation: A B/H C D E F G
Mainly used in Anglo Saxon countries (and so in jazz), it uses the letters of the alphabet:
A – B- C- D- E- F- G
The German alphabetical music notation
The German music notation uses a H and not a B (SI in alphabetical notation):
A – H- C- D- E- F- G
Music notation and countries
Syllabic musical notation is used by Italian, Portuguese, Greek, French, Russian, Flemish, Romanian, Spanish, Hebrew and Turkish people.
Alphabetical musical notation is used by Anglophone countries.
German Alphabetical notation is used in Germany, Poland, Russia, Scandinavia.
Correspondence between the name of the notes