Round-Robin DNS
Publishing multiple A or AAAA records for one hostname so resolvers return them in rotating order, providing crude load distribution across servers.
Round-robin DNS is the simplest possible load balancing: list multiple A records for the same name, and authoritative servers shuffle the order in each response. Clients usually try the first IP, so traffic spreads across endpoints over many lookups. It is cheap, requires no extra infrastructure, and works with any DNS provider. The big caveats: there is no health checking (a dead IP keeps getting handed out until you manually remove it), TTLs and resolver caching skew the distribution, and a single client can stick to one IP for hours. For anything beyond hobby use, GeoDNS, anycast, or a real load balancer beats round-robin.