What are static residential proxies?
A static residential proxy is an IP address that an internet service provider has registered as residential, routed through stable datacenter infrastructure. Target sites see a normal home-user IP, but the connection has server-grade speed and stays on the same address for as long as you hold the proxy.
That combination is why they are also sold as static ISP proxies or ISP proxies: the IP belongs to a consumer ISP's range, not a hosting company's, so it passes filters that flag datacenter ranges — while avoiding the instability of IPs borrowed from real end-user devices.