Although the names are similar and often confused, these properties are different. If you confuse them, the help for your PowerShell commands and modules won’t work.
The HelpUri property stores the URL (http or https) of online help for a command. It’s a property of commands (cmdlets, functions, workflows). When a user runs Get-Help -Online, Get-Help opens the default browser to the HelpUri property value.
The HelpInfoUri property of modules stores the URL of the online location of the HelpInfo XML file that enables updatable help for the module.
In fact, a non-null value of HelpInfoUri indicates that the module supports updatable help. The updatable help CAB files can be stored in the same location (or any online location specified by the HelpContentUri element in the HelpInfo XML file), but the HelpInfoUri URL always points to the HelpInfo XML file.