Localytics Place Entered is the event that fires when a user enters a Places geofence.
Localytics Place Visited is the event that fires when a user exits a Places geofence.
In most cases, enabling the Localytics Place Visited tag will be enough to collect all pertinent data for analytics purposes. An exception could be for extremely large geofences (like ones that include an entire city), where a user would rarely leave the geofence.
To get a better background on Places & geofences read up on it here as well as more information on Messaging with Places.