I like to think of punctuation in terms of driving metaphors, and in that case, the period would be the stop sign of the punctuation world. There are three different types of punctuation that we consider end punctuation.
The period is one of them, meaning it ends the sentence. Another is the question mark, and another is the exclamation point. So I'll give you an example from my favorite book. It's Ernest Hemingway's "The Sun Also Rises." The first sentence is, "Robert Cohn was once middleweight boxing champion of Princeton." So right there the period tells us to stop before we move onto the next sentence. I'll give you another example of a first line from a famous book. The book "Moby Dick" begins, "Call me Ishmael." It's a very simple sentence. It has a subject. It has a verb. It has a complete idea. And so we can give it some end punctuation with the period. One more instance when you might use a period is if you're abbreviating a word, and in that case a period isn't so much a stop sign as it is a way to signal that something has been taken out of the word and we're using a shorter form.
So for example, you might call me Mrs. Paterik. We use a period here. Same thing with Mr. Kahn, for example. You also might use it in street names. So if you have an address like 100 W. Spring, you'll use a period to abbreviate the word west. And you could also use a period to abbreviate the word street. So I hope that that gives you some ideas about how you use a period. Typically, it's used as an end punctuation to signal the end of a sentence, and it can also be used when you're writing an abbreviated word.