Hi@akhtar,
Ingress means when traffic comes inside your machine or nova instance. Say you have one web server hosted at port 80. To access this from outside world you have to assign one ingress rule assigning port 80.
Egress means when you try to connect with internet from the machine. For that you have to assign Egress rule, so that internet is accessible from Machine or nova instance.
Hope this will help.
Thank You