Today we're using conjunctions (and, because, so). Conjunctions are joining words (sometimes called connectives). They join sentences or parts of sentences together.
For example Dexter the dog chases frogs and Frankie the dog chases butterflies. And connects sentences of equal importance.
So connects two pieces of information. For example Dexter saw a frog so he chased it.
Because helps complete a sentence e.g. Dexter chases frogs because he thinks it is a game.