Garage is a place where you can add photos of your car. When someone adds photos for the first time an alert is added over the garage tab. At least that's how I believe it works.
Yep, just letting you know someone posted something new there. If you don't want to look at it, hit the little down arrow and click "mark viewed".
i have the sme thing, well i know what it stands for, i always just have a little 1 on the garage tab, even though ive viewed everything, its annoying and i have no clue how to get rid of it