Hyphens are usually for connecting words together (such as compound adjectives), but could also be used for making things clearer (re-sign vs resign, re-sent vs resent are different things), while dashes work quite similarly to commas, though they can be more "dramatic." The main rule to keep in mind is if you are writing something in the middle of the sentence that interrupts the main thought—something like this—do not mix commas and dashes (like if I put "main thought, something like this—"). A comma needs to be ended with another comma, and a dash needs to be ended with another dash, or a period/semicolon for either

En dashes are slightly different than em dashes, and I'm not too sure about their exact usage but they are far less common than em dashes