Here's what the web interface looks like. In the middle you see the website tree. I actually have two websites in my database. This is a nice thing about TYPO3: you can manage any number of websites from one database and share information between your sites.
In the right window you see the content for the selected page. In this case, you see the CMS representation of the page you're currently reading (well, an older version of it ;-)
Click on the pencil icon of a content element to edit it. Some of the available options that you see here are:
Text Editing - IE6 users can use the WYSIWYG editor for easier HTML editing. Others can use HTML tags.
Image Upload - TYPO3 takes care of server-side image resizing of all your graphics.