Abilities can refer to several things.
In The Witcher, there are basically three kinds of abilities and some statistics which can affect them.
Geralt has some basic abilities that he uses just to interact with the people or NPCs he meets in the course of the game. These are called character interaction abilities, and they include:
Geralt can acquire numerous witcher abilities by allocating talents gained through experience. These are called character development abilities, and they include:
There are also factors which govern how well Geralt can perform some of the skills he has, particularly in combat. These are called character statistics and they include:
In The Witcher 2, there are distinct abilities which modify Geralt's statistics. The base abilities, or attributes are:
Geralt can acquire many unique witcher abilities by the allocation of talents that he gains through experience. These are called skills, and they include:
See The Witcher 3 abilities page