Subordinating Conjunctions

A subordinating conjunction is a word that is a secondary conjunction used to make a transition from one statement to another smoother. (See, FANBOYS)
FANBOYS are transitioning words, specifically: For, And, Nor, But, Or, Yet, and So. These help us get a smooth transition between sentences and paragraphs that are about two different subjects. They are important in our writing and reading because of the smooth transition that they provide, without which it would be very rough writing and reading.