The path component must begin with a /.
After that, it may subsequently contain any combination of the * wildcard and any of the characters that are allowed in URL paths or query strings. Unlike host, the path component may contain the * wildcard in the middle or at the end, and the * wildcard may appear more than once.
The value for the path matches against the string which is the URL path plus the URL query string. This includes the ? between the two, if the query string is present in the URL. For example, if you want to match URLs on any domain where the URL path ends with foo.bar, then you need to use an array of Match Patterns like ['*://*/*foo.bar', '*://*/*foo.bar?*']. The ?* is needed, rather than just bar*, in order to anchor the ending * as applying to the URL query string and not some portion of the URL path.
Neither the URL fragment identifier, nor the # which precedes it, are considered as part of the path.
Note: The path pattern string should not include a port number. Adding a port, as in: http://localhost:1234/* causes the match pattern to be ignored. However, http://localhost:1234 will match with http://localhost/*.