Linux, Technologies ideas: How firefox is working & know the DNS ?

How firefox is working & know the DNS ?

/etc/resolv.conf file is used to inform to firefox about the DNS server ip address.
This file contain the list of DNS IP address, using this IP address firefox send the DNS request to get the IP for given web page(Eg: google.com)
resolv.conf is the name of a computer file used in various operating systems to configure the system's Domain Name System (DNS) resolver.

While user give "google.com" and enter, first it will check the cache, if it cache contain this then load from cache.
Suppose first time we are giving, then cache dont have this information.
So it tries to resolve the "google.com" string into an IP address,
To conver IP address, firefox uses the DNS protocol,
As mentioned above it will get the DNS IP address and request DNS for google IP address.
Once it get the google.com IP address, then it will start the session to that IP address using TCP syn,
Google will reply back with Ack+syn,
Again firefox replay the ACK, now 3 way handshake is over and it will get the page from google and will load.
Usually google.com doesn't give only one flow, many flows (connnection) will be used to load the single google page.