The search command,
/, is actually a motion, which means it can be used with operators. Any operator can be combined with search just by typing the desired search and pressing return.
For example, when in Normal mode,
d/,<CR> will delete up to a comma. Although
dt, would be more efficient, there are times when a search is more specific and useful than the other motions.
Much like last week's HTML editing with text objects, understanding how this works in terms of Vim's grammar gives you a greater understanding that can improve your productivity. The lesson is simply that
/ can work as a motion, because motions are just instructions that move the cursor in some way.