What is the exact difference between mongod and mongos

Question

While I was looking into the MongoDB documentation, I found two different terms mongod and mongos.

While starting the server, I am using

Answer 1

mongod is the daemon, mongo is the client, mongos is the 'MongoDB Shard Utility'. Take a look at man mongos:

mongos for "MongoDB Shard," is a routing service for MongoDB shard configurations that processes queries from the application layer, and determines the location of this data in the sharded cluster, in order to complete these operations. From the perspective of the application, a mongos instance behaves identically to any other MongoDB instance.