Group email

There is no way to create a "contact group" using the Contacts app on iOS.

You need to create the "group" on your desktop / laptop and then sync the "group" over to your iOS device at which point you can use the "group" to send an email to a bunch of people. When the Contacts app on iOS detects that you have a "group", a "Groups" link will show up in the upper left hand corner allowing you to access and manage the groups you have.

Once you have the groups setup, the Mail app will be able to access them just like an individual email address. Just start typing in the "group" name in the To: field, for example.