You can add different types of content to a page or a post. These contents can perfectly coexist, for example text, images and videos. For the latter, please refer to the corresponding help pages.
You can type text but you can also paste it. By default when pasting text, WordPress will keep some of the formatting that matches web standards and delete all the others. Formats that are kept are : bold, italic and links
Formatting the text
You can format the text by selecting it and then using the available tools.