The bottom portion of the Abilities Panel displays your trade skills. This will include your primary trade skill, any secondary trade skills you can train DFO Gold, and the base skills associated with them.
For example, if you're an Armor-crafter, you'll see Woodworking, Leatherworking, Cloth-working and Metalworking, while an Alchemist will see Herb-craft, Jewel-craft and Gem-cutting. All characters with a trade-skill will see the Siege-craft skill listed here, as well.
Combat Styles Panel: Just as spell casters get spells, all melee classes receive combat styles. These styles are based on the character's skill specialization. Arms men who use the Pole arm skill, for example, will receive combat styles based on the pole arm. The arms man will still have natural skill in other weapons, but may not have styles if the weapon type is not specialized.
To use combat styles, drag the icon from the Combat Styles Panel to your quick bar. Clicking on the icon (or pressing the appropriate number on the keyboard) while it is in the quick bar will set the character into combat mode and attempt to use the selected style on your next available attack.
If you've trained any realm abilities, they'll appear here as well. If any ability doesn't show here, it's not something you can use. So, a Shadow-blade cannot equip armor greater then leather (such as Studded or Chain).