You can review RadEditor for MOSS for MOSS 2007 or RadEditor for SP2010 for SharePoint 2010. You can find information on the controls in the following online help articles:
If you want to place the control in a custom solution we recommend using respectively MOSSRadEditor or SPRadEditor (for SP2010) classes, which are part of RadEditorSharePoint
Also you should know that these controls are based on RadEditor for ASP.NET AJAX. You can test it in the following online demo: http://demos.telerik.com/aspnet-ajax/editor/examples/default/defaultcs.aspx
Regarding the images here is the help article where you can find more information: Image Manager
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