explanation of the -3 and +12 on football games?

I am new to sports betting and would like to know obivously the absolute basics as in this and whatever elese there is. Thanks in advance.

[MCS]

If you see a line like "Atlanta -3" then it means Atlanta is favored by 3 points. A bet on them will win if they win by >3, push if they win by exactly 3, and lose if they win by 2 or 1 or they tie/lose.

Think of "-3" meaning you subtract 3 from their score. Like they start the game down 3.