Ticket types are the prices you offer for an event - e.g. General, Early Bird, VIP, Concession. You add them in the Pricing section of the event editor.
In the editor, open Pricing.
Select Add price.
Give the price a name, an optional description and a price (or mark it free).
Optionally limit how many tickets can be sold at each price (e.g. a capped Early Bird).
Customers choose between your prices at checkout. For seated events, you can also charge different prices for different parts of the room - see Zones and pricing.