TkDesk provides you with an application bar for fast access to your favorite applications, commands, directories etc., plus displays for the current date and time, system load, and the status of your mailbox and dialup link. It consists of an arbitrary number of buttons. Each button (also the aforementioned displays) contains a popup menu which can be accessed by pressing the right mouse button over any of them. If you single-click the left mouse button over such a button, the first entry from the corresponding popup menu defining a command to execute will be invoked.
The first button (displaying a small desk by default) could be called TkDesk's "Start Button". Its popup menu contains entries for accessing TkDesk's most often used functions, such as executing a command or opening a file list or browser window, plus submenus for your bookmarks, the files you most recently opened, and the directories you've last visited. The next entry is a submenu labeled "Application Bar". Here you can configure all aspects of the application bar, especially its position and orientation. See my answer to the MFAQ How can I change the position of the application bar? for more. The last entry labeled "Configuration" contains another submenu which gives you fast access to TkDesk's configuration files.
The second button gives you access to this User's Guide, and lets you view manual pages, also making use of a running TkMan (which is a hypertextified manual pager which is to be highly recommended). This button also allows you to drop executables on it to automatically display their manual page, if they have got one. Note that the default value of the "Manual Page" dialog is the contents of the current X selection, so this can be used for some sort of "context sensitive" help.
Keep in mind that all the buttons can be configured by you! See section Configuration of TkDesk for details on how to do this.