There are several Display Locations that you can choose from when creating a field (as shown below in the image).
Tabs 1-5 are content tabs set on a per category basis. If you have a category that has any content tabs, you can create fields that will display only on those tabs.
Own Tab is a TYPE of custom field (used in cases when you need more content tabs.. eg, you used up tabs 1-5 for a spcific category and you need more tabs, you use the OWN TAB custom field.
Self Placement (Only Showcase and AMS have this type of field) gives you the ability to place that field anywhere you want to.
You can also choose whether or not the field displays on Article View listing.
There is no other addon that has this many display locations and flexibility (cept my Article Management System) for custom fields (not to mention that Showcase (and AMS) both have Review Fields as well).