Both RadTooltip and RadTooltipManager can display rich content (including user controls and other ASP.NET controls), as well as AJAX-generated content. RadToolTip is meant to "tooltipify" a single element while RadToolTipManger should be used in scenarios where many elements would require a tooltip. For more information on RadTooltip, see the Overview topic.
Three common scenarios where the RadToolTipManager is useful:
When the developer wishes to 'tooltipify' all HTML elements on a page. This is the scenario where the developer already has a page with existing tooltips that need to be easily converted to a more refined, consistent look (using a particular skin or animation effect). RadToolTipManager overrides the standard tool tip behavior automatically just by including RadToolTipManager on the page.
When a list of elements should be tooltipified. In this case the RadToolTipManager TargetControlscollection should be used. This scenario allows for finer tuning. You can use more than one RadToolTipManager, each configured for a specific set of controls.
When one or more elements should display rich dynamic content that is fetched from the server. This approach is useful in cases where content should be fetched from a data source, depending on the element being targeted, and helps keep pages smaller. Use the OnAjaxUpdate event to populate tooltips from the server on-the-fly.
For a live demo of RadToolTipManager see the RadToolTip versus RadToolTipManager demo.