question regarding email

I have a MacBook Pro with OS X Yosemite 10.10.3. My question is , when I click on my email stamp and the window opens I click compose. When I enter for example letter a, several email address appear and I have no idea who all these peoples address are that appear . For me to remove their email address I click on remove from previous email list, then I click on remove address, all to delete them. Is there a way that would be easier to remove these address thats a little quicker, Thanks