Gru told his minions to go shopping since he is too busy with his master plan. He won't have any time to do the grocery since he need to think about world domination. The minions immediately went to the market to get some food for the ref, so all of them can eat something. This is one of these day that they need to go out and do the shopping as Gru is too busy with his world domination plan and can't attend to their needs. They need to prove to Gru that he can rely on them somehow. Their master would really appreciate it if they can do it on their own.
The using is using a bike in this game and you need to help him park his bike outside the store to do some shopping. There are no time limit in the game and you can finish the game in the least possible time that you want. Drive with care and try not to hit anything along the way. The game would be much harder as you make some progress. Try not to hit anything along the way as that might mean the end of the game for you.