The Online Checkout links are direct links that you can send to your customers directly and/or post the link on your website to direct registrants to this page. First you would need to find the event that you need links for and select the event. From the Event Detail page, find the drop down box next to text that says "I want to:" and select "View links to online registration." From here, you are brought to two different links.
The first link labeled "Event Detail" will bring you to your organization's public page that lists information about the event. This is helpful in having a detailed view of your event and allows for current and new registrants to purchase tickets. The second, "Direct Checkout" link, will give a page where a registrant will not need to complete a registration form in order to purchase tickets. Let's go over a bit about the "Direct Checkout" page.
When your registrants arrive at the direct checkout page for the event, they will see the event details here with the description down below. They will be able to choose quantities for the types of tickets you have for sale and will be able to update the quantity of tickets. All a registrant needs to do on this page is to verify the correct ticket types and quantity, fill out their "Billing Information", and click on the "Complete Purchase" button. That's it!