This is the {{If talkspace of}} meta-template.  It is used to customise a notice when it is being put on the talk page of a page.
Usage
This template usually takes two or three parameters:
{{If talkspace of |(pagename) |("then" action) |("else" action)}} 
Namespace and pagename-detecting templates  | 
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| Namespace |  | 
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| Pagename | | When on basepage | Detects and acts according to whether it is on a basepage or on any subpage (that is, a ../.. subpage).  | 
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 | When pagename is | For pattern matching on the pagename.  | 
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 | Module:Page | Can take apart and put together pagenames in several ways.  | 
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 | IP-talk | Returns IP-user talkpage, registered-user talkpage or non-user talkpage.  | 
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 | IP-user other | For detecting IP-user pages.  | 
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 | Subpage other | Pagename has an after-slash part (not in mainspace)  | 
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 | Sandbox other | Page is subpage /sandbox (template space)  | 
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 | Testcases other | Page is subpage /testcases (template space)  | 
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 | Rootpage other | Page is rootpage (vs. /subpage) (template space)  | 
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  | 
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| Others | | Stub other | Detects whether it is on a page with a stub template or not.  | 
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 | Redirect other | Detects whether it is on a redirect or not.  | 
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 | If preview | Detects whether page is viewed as a preview or not.  | 
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 | If IP | Displays different content to IP users and logged-in users.  | 
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 | If autoconfirmed | Displays different content to autoconfirmed and non-autoconfirmed users.  | 
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 | If extended confirmed | Displays different content to extended confirmed and non-extended confirmed users.  | 
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 | If administrator | Displays content only to admins.  | 
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 | If mobile | Displays different content to mobile users and desktop users.  | 
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 | If dark | Displays different content to dark mode users and light mode users.  | 
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 | Noscript | Detects whether page is viewed with a JavaScript-capable client or not.  | 
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