Why and when will the Maintenance light come on? Is it simply based on mileage? CEL is the one that actually indicates systems malfunction/failure right?

My maintenance light started blinking today on my way back from work, but after a few blinks, it went away. Should I be concerned? Or is it simply telling me that the mileage indicates I should be getting service soon?

And yeah, I tried the search function but it's not working right now.

 

Nevermind, search function is working again. Apparently I answered my own question already.