Parallelism

Parallelism is a series of related words or a list of items. Nouns are listed with nouns, words ending with -ing are listed with words ending with -ing, and so on. The secret to parallelism is to make sure everything is the same.

For example:

My plans for tonight are shopping, seeing friends, and watching movies. 

When I get home, I am going to eat dinner, do my homework, and go to bed.

 The previous two examples show parallel construction as in the 1st example, all the words ended with -ing, and in the 2nd example, all the verbs were in the infinitive form.

I am going to see my friends, take a test, and helping my mum with chores this week.

This sentence is not parallel because the 1st two items on the list are verbs in the infinitive form, and the 3rd item is in the -ing form.