The Total Events field in the User Export is used to determine the Top People in your namespace. This field keeps track of the total number of events that the user has completed in your app. For example, if a news app has 5 events (i.e. read an article, save an article, share an article, comment on an article, or watch a video), and the user has read 54 articles, shared 10 articles, saved 6 articles, commented on 3 articles, and watched 27 videos, the Total Events for the user in the app would be 100.
This field provides valuable information for campaigns as it provides the basis for Top People, which can be used as a Target Audience for a One-Time campaign. For example, let's assume that for the same fictitious news app in the previous paragraph, the user who has completed 100 events in the app is one of the Top People. You could send him a one-time campaign giving him a discount on a subscription.