It is possible to hide almost every record from other users or protect it from changes. Only the owner of this record (the one who created it) and the administrator can set access rights. The administrator can edit any record, see hidden records and change the owner.
When you open a transaction for editing, you can find the button with the lock in the lower left corner of the window. Click this button to open the menu where you can set access rights. Also you can assign access rights to multiple records at once using batch editing.
Owner
Change entry owner (available only for the administrator).