What does "the song released" exactly mean?

1. What does “a song is released” specifically mean?
does it simply mean a song “made available to public”?
so in terms of indie, or DIY, if I put one of my songs/compositions on Myspace, or Youtube, does that mean I’ve just ‘released’ my single?
or it’s not as simple as that (ie: there’re other factors involved?)

2. Why it seems that the “major release” records, or a single, usually gets into music charts, eg: UK Top 20, Italian Top 50, Billboard etc etc, while “indie release” record/s, from what i’ve observed, seems to never gets or ‘breaks’ into those music charts?
what do you think is/are the biggest factors determining that?

3. Any most, very practical advices on how, if I want to start seriously releasing my compositions (thinking of releasing an EP/mini-album of my instrumental compositions) in indie/DIY way, what are the practical steps i have to do now by myself?
thanks!