Exhibition preparation - What is an artist biography for someone in the early stage?
It's difficult to answer this without knowing the specifics. But what I can say is that a gallery will look for some kind of narrative that ties your experience as an artist together. Generally you should include your most recent/most prestigious shows from the past, and then draw a connection between your former work and your current work using the time you spent not exhibiting. 

Is there something you studied during the time you weren't showing work that has influenced your current work? Don't dwell on it, but do mention it. I find that art lovers have a positive view of artists with interests outside of the arts, so I'm sure you'll be able to massage some nice sounding narrative out of whatever you were doing.