Onto abilities–these are exactly what they sound like, special abilities that you can use during combat. You can customize your characters’ abilities from the Ability option in the main menu. Abilities are divided into three types.
Command abilities are triggered from the Ability option in battle and can do a variety of things, such as do extra damage to the enemy, cause a status ailment, recover HP or maybe even a mixture. These types of abilities may come with a cost, whether it be MP, BP or something else entirely.
Any one character can have two sets of Command abilities at one time–their Fixed Command, which includes all the available Command abilities from their current job, plus the Job Command, which has all the available Command abilities from any job of your choice.
As you can probably imagine, Job Commands are excellent for personalising your characters and developing crafty battle strategies. Want a Black Mage who can also heal? Sure, just set his or her Job Command to the White Mage’s White Magic.
Support abilities are a different beast altogether; unlike command abilities, these work passively. Each Support ability has a cost (the early ones all cost 1 point) and you can equip as many Support abilities as your character’s Support ability cost limit (initially 1 point, so you can only equip one Support ability costing 1 point).
You can equip support abilities from any job regardless of your current job. For example, you could be a Knight with support abilities from a Monk and/or White Mage. As the game progresses, your characters’ cost limit will steadily increase (up to a maximum of 5 points), so you’ve another gigantic window of customization.
Finally, each character has a Specialty, which is again based on their job–this is usually just a Support ability that’s always present. Most jobs will learn their specialty as a support ability too at higher levels, so specialties don’t stay special forever, sadly.
You can gain new abilities for your characters by levelling up your jobs with Job Points (JP), earned from battle. For example, White Mages learn the Magic Defense 10% Up ability at Level 2. Note that only the character’s current job will gain JP.
So if you want to learn a variety of abilities, you can’t stick with the same job. However, sticking with a job has its benefits too, as higher level jobs will raise your stats more–if you’re training new jobs from scratch, be sure to keep some characters in higher level jobs for support.