Consul
In plain terms
A tool for service discovery and configuration.
Going deeper
HashiCorp Consul enables services to find each other, performs health checks, and stores shared configuration across a network. It connects and monitors services.
Under the hood
Service mesh, KV store, and health checking in one; supports multi-datacenter setups.
Examples
Service discovery, health checks, service mesh, config store, microservices.
Think of it like...
Like a constantly-updated directory telling every service where the others are and if they're healthy.