Focus has multiple meanings in the study of magic.
A focus component funnels the magical energy for some spells. The spellcaster needs to manipulate the focus as part of the casting process. Foci tend to be expensive, though some casters have alternatives to use, such as divine spellcasters who may substitute material components of a spell with their religious symbol acting as a focus component.1
Focus spells are unique to each specific source of training, such as a class, and reflect their individual features.2 Focus spells can be categorized into types closely tied to each respective class, but in rare cases a given class's type of focus spell can be learned through other means. For example, sorcerers cast bloodline spells, but dragon disciples can learn to manifest some of draconic-bloodline sorcerers' same spells; and clerics are the most iconic and diverse domain spell casters, but these techniques can also be found to a certain extent among such magic users as champions, shadowcasters, and Bright Lions.