A parking scheme favoring residents of an area over visitors. Local residents apply (and pay) for long-term (usually annual) permits and signs are erected explaining that if you don't have one of these you are subject to towing.

Residential users love it; commercial users hate it. Residential users vote locally, therefore permit parking sprouts up like a weed everywhere. Often the ultimate winners are the private valet parking operators (who get lots of business) moving companies (for all the businesses that try and fail in permit-plagued areas) and of course city officials (who get to collect not only the permit fees but also the parking fines and towing fees).