The data in Gmail or other Google products is Big Data. Gmail uses Distributed Storage for structured data. It helps to manage the data easily.
Gmail itself is a portal for logging in. It contains the database of google ID's and passwords. A user can log himself into using the right credentials.
yes it is possible beacouse in the gmail database there are in no record of that user
You cannot just retreive the email database. It is the private property of the Gmail users. Moreover it is guarded by the protocols of Gmail.
Use Gmail notifier
Yes, you can use gmail on the iPad.
why would you use database?
Yes you can use gmail as a back up email server. It si necessary to enable IMAP in gmail before using gmail back up.
McDonald's use database for...
Yes, a company server save Gmail emails. The company server could save the internal mails. Moreover it can also save promotional mails in the database.
no
They use Gmail, an email website to Gmail chat with their other friends who have gmail. They use IM programs. They use Facebook, myspace and Twitter to communicate with known and unknown people.
you can use your hotmail acc too... it is not necesary to use Gmail... AOL is oso accepted...