Parallel construction means using the same pattern or structure of words.
For example, in the sentence: "I went swimming, hiking, and sledding" the actions swimming, hiking, and sledding are all in the same structure -- they are parallel.
First, a writer would use parallel construction for better clarity. Writing that does not use parallel construction is often confusing and poorly written.
Secondly, a writer would use parallel construction to indicate ideas that are equally important.
