First your computer needs to know where google.com is located so it will ask your DNS server. Where is google.com. located (on what IP address).
So it will use a Recursive request. This means your computer says :
give me the ip address or give me an error.
Your DNS servers says "Hm.. ok boss, i'll go and find what you seek"
The DNS server then will use an iterative requests which typically means he will request the root server with "Give me the ip address of google.com. or give me a server who has more info for me.
So, your DNS server will request to the root dns server of the internet for the A-Host record of google.com.
The Root doesn't have the A-Host for google.com. and will reply with "I don't have the google.com. A-Host, BUT! I do have a server who has more information for you. It's the .com. DNS server which is located on *ip address*"
Then your DNS server will request the same to the .com. server
and probably then the .google.com server which will in its case give the IP address of the A-host record of the site you wish to visit.
After you receive the ip address of google.com..
Your computer will send a message to the ip address of google to request the website.
This will be routed. First through your standard gateway and then it will be following a path which is defined in the routers.
It can be explained in much more detail, but this is typically the way.
Any response to a DNS query that originates from a DNS server with a complete copy of the zone file is said to be an 'authoritative response'. What complicates matters is that DNS servers cache the answers they receive. If a DNS server has an SOA record, it fills in a field in the response that signals that the server queried is authoritative for the domain and that the answer is authoritative. Any DNS server external to that domain that retrieved the authoritative response will cache that answer. The next time the server is queried, it will say that the answer it is giving is authoritative, even though it is not authoritative for that domain.
In other words, it IS possible for a DNS server that is NOT an authoritative server for a domain to give an 'authoritative response' to a DNS query for a domain it does not serve.
Non-authoritative responses come from DNS servers that have cached an answer for a given host, but received that information from a server that is not authoritative for the domain.