Digital Distribution services get your music to 1 or multiple online stores and streaming services all at once. Without these services you would need to upload your music, artwork and accounting to each store individually and in most cases the online stores (like iTunes) dont provide a direct submission storefront at all.
Here are links to some of the main digital distributors:
To submit your music you will require:
- Your music in 16 bit WAV format (CD Quality). Mp3 will not suffice
- Your song or album artwork in digital format. The cover pitcure should be exactly square in dimensions and submitted at high resolution quality
- A credit card or method of payment