Conjunctions are words that are parts of speech that are vital in making the English language readable. If there were no conjunctions, you would read text something like this:
"Jack went up the hill."
"Jill went up the hill."
Now read the sentence: "Jack AND Jill went up the hill."
The word, AND, that joins the two sentences into one larger sentence is known as a conjunction. Conjunctions are joining words that join two words or two phrases or two clauses. There are three types of conjunctions - coordinating conjunctions, subordinating conjunctions and correlative conjunctions.