1.1.1.1 is marketed as the fastest public DNS resolver and commits to not selling data and purging query logs within 24 hours (audited by KPMG). It supports DNS over HTTPS (https://cloudflare-dns.com/dns-query), DNS over TLS and the WARP app. Secondary: 1.0.0.1. IPv6: 2606:4700:4700::1111 and ::1001. Malware-blocking variant: 1.1.1.2; family filtering: 1.1.1.3.
The address was notoriously "dirty" before Cloudflare adopted it: many routers, captive portals and internal networks had used 1.1.1.1 as a placeholder for years, so Cloudflare still receives a large volume of junk traffic. If 1.1.1.1 does not resolve on a hotel or office network, the network equipment is probably hijacking it.
Like Google's resolver it is anycast; geolocation databases point it at Cloudflare's registration (San Francisco or Sydney via APNIC) rather than where it answered.