:target Selector
Selects the target element indicated by the fragment identifier of the document's URI.
.target()
If the document's URI contains a fragment identifier, or hash, then the :target selector will match the element with an ID that matches the identifier. For example, given a document with a URI of https://example.com/#foo, $( "p:target" ) will select the <p id="foo"> element.
Further discussion of this usage can be found in the W3C CSS specification.