"no keepalive" and "no shutdown" command on router and switch interface

Networking
1

What’s is the difference between no keepalive and no shutdown ,
no shutdown command to keep the interface ‘UP’
no keepalive for ???

2

The Interface check the other end is up or not based on keep alive messages,
If you stop keepalive messages on router.

They dont understand if the other end of the interface is up or down !!

No shutdown is a command to enable the interface.