svnlook is a command-line utility for examining different aspects of a Subversion repository. It does not make any changes to the repository—it's just used for “peeking”. svnlook is typically used by the repository hooks, but a repository administrator might find it useful for diagnostic purposes.
Since svnlook works via direct repository access (and thus can only be used on the machine that holds the repository), it refers to the repository with a path, not a URL.
If no revision or transaction is specified, svnlook defaults to the youngest (most recent) revision of the repository.