Daily Ops features a number of objectives that you can complete daily to earn bonuses. If you're able to complete each objective in the time limit, you'll earn the Commander Objective for an extra bonus.
Your objectives are drawn from a pool every day. If you're unable to complete a particular objective, ie. you've purchased every bullet skin and can no longer purchase one to complete a particular objective, then that objective will not appear in your daily list until it is possible to complete it again.