The demo represents a WYSIWYG HTML editor with a Signature Dialog that allows users to insert a handwritten signature into a text editor. The dialog is opened by clicking on a custom button called "Insert Handwritten Signature" in the Telerik RadEditor. The dialog displays a signature pad that allows the user to draw their signature. Once the user is done, they can click on the "Store on Server as PNG and Insert" button to store the signature on the server as a PNG file and insert the signature image into the editor.

The Default page contains the RadEditor control with the custom button defined inside the tool groups. The InsertSignature.aspx page contains a RadSignature control that provides the signature pad functionality. The codebehind file of the InsertSignature page handles the AJAX request and saves the signature as a PNG file on the server.

You can find more information of how to build your own RadEditor dialogs in the Custom Dialogs demo.