You can use the statistics page to keep track of participant activity in your events. Lyyti identifies each participant by their e-mail address and forms statistics of their registrations per email address (i.e. the same physical person can appear as two separate participants in Lyyti, if they use different email addresses, this is good to bear in mind).
The activity statistics tell you how many events your participants have registered for, or whether they have or have not reacted to your invitations. This is also where the statistics show up when you take attendance at your events, either with the Lyyti mobile app or by manually checking people in. The different states of attendance are: