Use + to separate mails

Gmail filters can separate mails sent to name+someword@gmail.com and
name+anotherword@gmail.com.

Two examples:
1.Give your Gmail address to Amazon and Ebay as name+amazon@gmail.com
and name+ebay@gmail.com respectively and filter the mails from Amazon
and Ebay.
2. Make special address like name+love+special+somebody@gmail.com for
that Special Somebody to write you.