Fetch and Update

Fetch and Update

Greetings All,
 
Can someone point me to a clear explanation of "Fetch and Update"? 
 
The link http://help.creator.zoho.com/Fetch-and-Update-Records.html is extremly vague.
 
Senario:
 
I have one form that will be storing data.  I will be using a different form to collect data.
 
My work is as follows:
 
1.  Complete "Form A"
      "Form A" will have several fields that will not be completed initially.
 
2.  "Form B" will be processed multiple times.
      Each time "Form B" is processed, I will need to update cooresponding records and fields in "Form A".
 
3.  I intend to fetch a single record from "Form A".
 
4.  Once the record has been fetched it will then be updated with new data.
 
5.  Once the record has been changed, I need to update.
 
I have gone through all of the forums and help, but find the instructions vague and confusing.
 
Thanks in advance.