Dropbox keeps a record of information about your main Dropbox folder and your shared folders. This information is saved in files named ".dropbox" in the root of your Dropbox folder and the root of your shared folders respectively.
You will not see these files unless you enabled the ability to view hidden files and folders in your operating system.
We strongly recommend against removing any ".dropbox" files. Removing these files can cause you to leave shared folders unintentionally. Removing ".dropbox" files can also duplicate shared folders in your Dropbox.