Hi,
In resource file you can set the caption and that caption can be used from entire web applications. Set the name as id in resources and value as caption. You can provide a comment if applicable. Example:
<asp:label id="Label1" runat="server" text="<%$Resources:Common, lblActiveWorklist %>"/>
Here,
Resources - Is the keyword to access the resource file.
Common - Is the name of resource file
lblActiveWorklist - Is the id of the resources of which caption you want to access.
All the best.