Within the events module, you are able to send two different types of emails to members, contacts and registrants, namely Invitations and Emails.
Sending an Email
Click on the Events or the Calendar icon on the left.
Click Manage on the event you would like to send an email for.
Click on the Email tab. You will see two buttons: New Invitation or New Email.
New Invitation - Allows you to send an email to invite members and contacts to register for the event.
New Email - Allows you to send targeted emails to registrants and attendees, based on options such as tickets and products purchased, registration questions answered, etc.
After selecting your desired option, create the email and send it to the desired recipients.