Telegram app. Yeah, but how?

Telegram has so many features that I don't know how to use yet. For starters, I just can't grasp the difference between a group, a channel and a bot.

If anybody is interested, I could use some guidance. Lj seems to be telegram friendly, but the question is: just how many lj bloggers are there on my friends list who use it?

One of the groups I've created
https://t.me/tmtwngm received lj updates from Russian bloggers and I don't even know how I set that up; nor where to begin to tweet the @ljbot I must've somehow activated to achieve the blog updates.

I've received blog entries from

vg_saveliev
a_nalgin
el_murid
... but who even are these people?