EPESI is a collaborative application and as such everything is shared by default: contacts, companies, tasks, calendar events etc. When you create an event (meeting) on the calendar and assign it to yourself (default) it will be visible to other users if you make it public, and anyone will be able to change it. If you don't want this event to be changed, but still be visible to anyone you should make it public - read only. Finally an event marked as private will be visible only to users assigned to the event.
To see another user's calendar use the Perspective button. When using another user's perspective you will be able to see only his/her public and public read-only events. Private events are visible only to users assigned to it.
Perspective does not apply to recordsets like Companies and Contacts - in this case the button is grey (inactive).
There are other possibilities to restrict access to certain recordsets using Record Browser's Advanced Permission System but this is a complex subject. For starters the default options: public, public read-only and private is sufficient to control access.