Static websites are the ones written in plain HTML. Every page is a separate document and there is no database to support it. That said, the only way to edit the website is to go through each page and edit the HTML. You can either edit it yourself or hire a web development company for this purpose.
A dynamic website however includes complex coding and it can do a lot more for you. For example, it may have a login page and once you sign in, you may add information or products as in eCommerce stores. Each page is custom designed depending upon the information required in a database and this information can be altered via another user-friendly interface.