Under Services you have the option to create Services, Events or Add-ons. They are all offerings or types of appointments you offer, but they differ in the following:
1. Service - A primary service that you provide all the time. Examples of primary services might be as generic as "General Consultation", or as specific as "1 Hour Massage". Each service has a duration and optionally a price and clients can schedule for any time during your hours of availability. If a service is set to a duration of 1 hour, then your availability will be shown to your clients in 1-hour slot increments to choose from any time you are open to take appointments. This service is a one-on-one offering.
2. Event - An event is offered on specific dates and times. This will let you create a new event and define the schedule that you'll be offering it. You may offer this event on a specific day and it may never reoccur similar a one time conference, or it can be an ongoing event that customers can attend so it can repeat on specific recurring bases. An event can also be a one-on-one event or a group event. Group appointments allow you to have multiple people book for the same event at the same time. You can have an event that holds the same class every day like a spin class, or can be a one time event like a seminar. More on Group Appointments found here.
3. Add-on - An additional service is a service the customer can opt to add when booking. These are usually extra time, or an extra service that can only be done if a main service is asked for. An additional service can never be booked alone, but it can be set to a specific pre-existing service as an add on.