Hi Simran,
Deployment is about copying your .war file into the correct deployment-directory of your container (e.g. tomcat $CATALINA_HOME/webapps)
When tomcat is starting up it will startup/activate your wep-application.
When we restart Tomcat ( or any other Container) is everything redeployed ?
Yes, but you can even copy a new .war file on the deployment dir while tomcat is running and tomcat will uninstall the old version and install the new version.
have a look at the description tomcat gives:
Tomcat deploy
Regards,
Frits