Sentence types depend on the number and types of clauses. Words most often function in units, either phrases or clauses. A clause is a unit that contains a subject and a matching complete verb. A phrase is any other type of unit. See your text for a more complete list of common subordinating conjunctions.
Birds fly .
Birds fly and eat insects. Birds and bees love flowers and fly near them whenever possible . A simple sentence can have any number of modifying words and phrases. On bright, sunny mornings, small birds and buzzing bees dearly love fragrant and brightly colored flowers. Birds can fly , but cats can jump .