Market segments are the area of the market a given company is attempting to enter. Normally, one might think of this as "aerospace" or "steel" but this is Shark Tank so the segments tend to be a little more pedestrian, like retail, and food.
Everything has to be categorized, especially on a site like Stats For Sharks, otherwise, what's the point in trying to analyze any of it. So companies have each been assigned a category or "market segment" whether we maybe had to shove a square-ish peg into a round-ish hole or not.
We also reserve the right to re-assign market segments to deals whenever we decide something might fit better elsewhere.