Archiving a lead will place that specific lead in your “Archived Leads” Queue until that company visits your site again. At that time the lead will be removed from the “Archived Leads” Queue and be placed back in your “All Leads” queue. IF this company does not visit your site again this lead will remain in your “Archived Leads” Queue. Leads that are archived will still count against your monthly lead quota.
If you want to learn how to archive your leads strategically, review this guide.