https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.webcontrols.repeater?view=netframework-4.7

A data-bound list control that allows custom layout by repeating a specified template for each item displayed in the list.

https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.webcontrols.repeateritem?view=netframework-4.7

Represents an item in the Repeater control.

Remarks

A RepeaterItem object represents an item in the Repeater control, such as the heading section, footer section, or a data item.

The data items of the Repeater control are stored in a RepeaterItemCollection object that can be accessed by using the Items property of the Repeater control.

You can use a RepeaterItem object to programmatically access the properties of an item in the Repeater control.

Docs-->.NET-->API reference-->System.?Web.?UI.?Web?Controls-->Repeater