what you already know about your topic.
Background research is not the information you already know if it were it would not be called "research". It's really additional information that you look up on your topic and a brief overview of some of the important facts.
background study of makeup
"By way of background" means getting to know something or someone by reviewing its past. The background will give you information on how a company operates.
... will you please give me some background about that...
Background colours
the preceding history that is at all relevant to whatever it is you are referring to
are you meaning who plays the guitar for the tracks in the background
Yes, "background" is a compound word, consisting of the words "back" and "ground" combined to form a single word with its own meaning.
Arda Denkel has written: 'The natural background of meaning' -- subject(s): Meaning (Philosophy), Naturalism
Genetic background which makes the arches in different patterns
his or her cultural background.
his or her cultural background
his or her cultural background.