Consul is a lightweight service to provide a service discovery registry with failure detection (health checks) for circuit breakers. It also provides configuration management with key/value storage.\ The typical way to use it is that a consul master cluster takes care of the update and write processes and consul clients run locally on the apps host - data is shared accross the complete Consul cluster. The data can be accessed by using DNS and HTTP APIs.
At AOE, we use Consul for settings distribution with consul-template as a way to do Settings Injection during deployment. Consul is also used as service discovery between apps inside microservice environments.
With Vault there is another tool that can be used to manage and share secrets.