Well, apparently if you sign up using google account you will have not one but two email address first one is your genuine xyz@gmail.com, the other is xyz@googlemail.com. But why does this important? Well, you can use it for some reason like :

1. Subscribe in yahoogroups or googlegroups using one of your google email and create a filter for those emails from group easier.
2. You can give for you VIP contact list a gmail.com email and the rest of your contact a googlemail.com address. This way you can separate each groups using filter and treat them differently.
3. You can give this treatment also for Business email and Personal email.

There is still some trick in gmail address, such as

1. You can give your email using dot like l.p.l.p.x@gmail.com or l…..plpx@gmail.com and it still sends to lplpx@gmail.com, but if there’s another account with l.p.l.p.x@gmail.com that email will be send to that person.
2. You can add plus sign like lplpx+test01@gmail.com and lplpx+test02@gmail.com and it send to lplpx.com as well.

Have a nice try.