They may be small words, but conjunctions are highly functional and very important for constructing sentences. As you can see in the first sentence the coordinating conjunctions "but" and “and” were used to link different parts of the sentence. This is the main job of conjunctions. Basically, conjunctions join words, phrases and clauses together.
There are three types of conjunctions: Coordinating, Subordinating and Correlative. Each type joins together different parts of a sentence. The chart shown here is a list of some of the most commonly used conjunctions.
Coordinating conjunctions like "and" "nor" or "so" link equal parts of a sentence, be it words, phrases or clauses. For example:
Subordinating conjunctions such as "because", "since" and "after" link a dependent clause to an independent clause, helping to emphasize the idea of the independent clause. For example:
Correlative conjunctions work in pairs to join equal elements of a sentence together, like "either/or", "such/that" and "not only/but also". For example:
Remember, the main job of a conjunction is to link together different parts of a sentence to help you connect or emphasize ideas, and form more complex and interesting sentences.
For more examples and details on the different types of conjunctions and their function in a sentence, YourDictionary has more articles describing each one: