Life can be hard when you have many things to do, and not much time to do them. If you can, it helps to be able to do two things at the same time. If you have to go to the bank and buy food for your house, you can do both on the same trip. This is called killing two birds with one stone.
Sometimes when people have too many things to do, they can find ways to kill two birds with one stone and make life easier. You can kill two birds with one stone by simply buying clip lock strap while going to the music store. Or maybe, if you are cooking a meal, you could kill two birds with one stone by making enough for dinner today and lunch tomorrow. Killing two birds with one stone is nice because it gives you more time to do all the other things you love.