Use this command to change the SVN-type of the selected files. The file type can be either a default Text, a default Binary or a Custom type. In case of a Custom type, you have to specify the corresponding MIME type here. E.g. 'text/html', 'application/pdf' or 'image/jpeg'. Don't change will leave all file types as they are currently.
The file types are relevant for some SVN operations, for instance updating, where in case of text types the line endings, etc. can be replaced. By default, when adding files (see Add), the file type category (text or binary) is automatically determined by SmartSVN. In general this detection is correct, but in certain cases you may want to explicitly change the type of the file by this command.