Abilities are what make characters unique. Abilities allow your characters to do more than just move and attack, over and over again. They give your player proficiency in useful skills, allow you to perform supernatural wonders, and to perform feats outside the realm of the ordinary person.
A player's abilities come from a variety of sources. Here are a few of the most common ones.
All characters start with proficiencies that represent the kind of basic training you have. These determine the kind of weapons you know how to use, the languages you speak, the kind of magic items you can create, and other basic skills. Proficiencies are very binary. You either know how to do something, or you don't. They usually don't enhance your current stats, or allow you to work supernatural wonders, but they do help determine how your character functions on the most basic level.
Skills represent abilities that most people have. They aren't limited to adventurers with elite training or supernatural capabilities. They determine how well your character can run, jump, climb, persuade others, hide, or intimidate. Some skills are knowledge based. These represent how much your character knows about a particular subject. Others, like picking locks or tracking, require a little extra training (proficiencies) before your character can use them.
Most of the abilities your character will use on a daily basis are granted by your choice of class. Spellcasting, using rage to fuel combat, knowing how to sneak attack enemies, the ability to change your shape into that of an animal, these are all powerful abilities granted by your class.
Some abilities are shared among multiple classes or are available for training as the character progresses. These common abilities are universal skills that, while common among some types of classes, are learnable by most everyone.
As characters progress, they can learn techniques that allow them to alter the way their abilities work. Techniques make existing abilities more powerful, more flexible, or simply more available. Characters can lean any number of new techniques, but for techniques to be effective, they need to be maintained through regular practice. As such, character have a set number of technique slots that represent those specific skills they have been regularly working to keep in usable form.
Regardless of their source, abilities fall into one of the following four general categories. These categories are mostly for reference and become mostly useful when trying to understand whether certain types of magic, like anti-magic fields or counterspells, affect your abilities.
Extraordinary abilities are non-magical. They are, however, not something that just anyone can do or even learn to do without extensive training. Effects that suppress or negate magic have no effect on extraordinary abilities.
Spell-like abilities, as the name implies, are magical abilities that are very much like spells except that they aren't "cast" using any components. Spell-like abilities have the following properties. They also can be interrupted during casting, requiring a concentration check.
Supernatural abilities are magical but not spell-like. With the following properties.