Trunk The trunk directory usually contains the most current development code
Branches The branches directory is usually used for branching. It contains copies of your trunk at various stages of development
Tags Tags are like branches, however tags are not to be used for active development. They mark (tag) a certain state in the code
Readme.textile This is a sample readme file. In Assembla you can use textile, html or markdown to add some sugar to your readme files. Just add the extension to your readme file to recognize the markup you want to use
This common SVN hierarchy is not enforced in anyway and you can change. If you are joining an existing project you might not find the same folder hierarchy described above.