Send e-mail to multiple contacts as as separate mails
As the previous answer states correctly, CiviCRM does in fact send individual emails to each contact you selected. The simplest way to know this is thats the only way tokens would work properly. If everyone was just to'd in one big list they'd all see one set of tokens (mail merge fields) which would not be correct.

If you wish to add others then you can using the BCC and CC fields but they'll get copied into every single email i.e. if 50 contacts are emailed then they'll get copied into those 50 emails.