They're focusing on the market below EventBrite, small free events and small venue (i.e. tech user talks) that may require a small fee.
It's really refreshing to be able to just say "I want to attend that event" and for it to be a few clicks rather than an arduous check-out process.
Note: Whilst they have a "browse" button at the top, they've started by providing stand-alone pages that act as a flyer and mini-promo site for the event... this is a tool with great potential, not a fully mature product. Example of an event page http://attending.io/events/how-to-market-through-influencers...