This tool searches for experienced* editors who have recently edited. Recent activity does not mean these editors are available to assist immediately, so check their recent contributions first to see if you would be interrupting. If your contact isn't around, try going through the normal noticeboards instead. When linking to this tool, put ?group after the URL to make it display recent users in group - available groups are everyone, admins, and crats.
This tool was designed as a replacement for WP:Highly Active Users, which sought to list active editors who could provide assistance or advice by timezone.