Tell me the Differences  

Hi yathini, welcome to Mylots!

I am no guru, but a firewall keeps certain sites and people from entering your computer without your permission.

Anti-virus protection will detect a virus when it enters your system thru a site or email.

This is very basic, but it is the best I can do!

Hi yathini. Welcome to mylot!
Actually they have completely different concept. But since they are both matter of security, sometimes they also have the other capabilities.
A firewall monitors your network communications weather harmful or not. Mainly if a program wants to send or receive packets from the network or internet, it warns you. You can configure it in several ways and create some rules for that.
An antivirus mainly based on the signatures of viruses monitor each executable before executing. and an internet security package is a combination of an antivirus and a firewall.
I hope it is useful.

a Firewall is a Feature that blocks internet virus from internet when you're browsing (online) it work like the magician's Firewall (imagine the virus go through the fire and get burned into ashes) it work just like that... if a virus want to get through into your PC, the firewall will detect and delete it.
and also, a firewall will protect your programs accessing internet automatically (the firewalls warn you or ask for your permission)
it is a wall between your computer and internet with protection that is firewall
but a firewall can't detect a virus that has already infected your system files

as for anti-virus, they're a program that can detect, quarantine and delete the virus that has infected your systems. Some of the anti-virus even work as firewall but not all of them. they work to protect and clean your computer from viruses.
now there are more feature depends on the anti-virus that you use..
ex: they can check any external storage that you have just plugged in to your computer, do a scheduled scan

that is why we need both of them to get our system secured safety

Anti Virus protect your computer from virus and virus infected files which are already in computer local drives.

Firewall monitors your internet connection.it block or allow a connection to internet or from internet.