Washing the car is called 'car washing' and doing the dishes is called 'dish washing' and mopping the floor is called 'floor mopping.' Things we do a lot of get this special wording. However, doing your homework does not get called 'homework doing.' Walking the dog = dog walking , but cooking the dinner doesn't get called 'dinner cooking.' I can't think of any grammar rule, but it's Saturday and I'm off out dog walking now. So I'll leave it to others to figure out a better answer! Bye!

It's called "parallelism". You need to pay attention to this if you want to give a list of things. Apart from that, I don't think it's a very good example for a textbook, and I'm a little disappointed to see it copied thoughtlessly across other (non-English) websites.