The Background Skills optional system splits skills into two categories: adventuring skills and background skills. Characters get a few extra ranks in the latter, allowing them to acquire skills that rarely come up during adventures.
Adventuring-oriented skills such as Perception are usually more important for your character's survival than background skills such as Profession, but these background skills are invaluable for fleshing out characters. This system separates skills into adventuring and background skills, so you don't have to sacrifice your character's life expectancy for her to have a rich background or engage in downtime activities.
The standard skill system has a lot of versatility. It allows characters to overcome various challenges related to their diverse talents, with simple rules for dealing with beneficial or adverse conditions. Though many players simply spend their skill ranks on the same skills at every level, it is also possible for a character to diversify his investment in order to gain access to more skills overall or to remedy a shortcoming.
However, not all skills provide the same benefit to characters. It's difficult to argue that a high bonus in a Profession skill has the same value as a high bonus in a more general skill such as Perception. Yet Profession is an important skill for nonplayer characters, as well as for players who wish to show that adventuring isn't the only thing their characters care about.
This system recognizes that skills such as Craft, Knowledge, and Profession serve an important role in the game. Though these skills don't directly affect the careers of typical adventurers the same way that Bluff, Perception, and Stealth do, they are useful means for characters to interact with and explore the world outside of combat. You shouldn't have to choose between having the knowledge to understand the world and the ability to survive in it!
These skills are called background skills because they reflect the non-adventuring interests and passions of a player character, or the skills more important to NPCs. All other skills are called adventuring skills.
In a campaign that uses the background skills system, each character gains an additional 2 skill ranks per level, which must be spent on background skills. More details appear in the Gaining Background Skills section. These new rules make characters and their skills more versatile, but because they boost non-adventuring skills, they're unlikely to unbalance a campaign.
Skill Changes
Appraise, Craft, Handle Animal, Linguistics, Perform, Profession, and some Knowledge specialties are all background skills. While all of these skills can be useful, or even necessary, in certain types of campaigns (such as Profession [sailor] in a nautical-themed campaign) or for certain types of characters (such as Handle Animal for a druid or ranger), they are often of less immediate value than sneaking up on a foe using Stealth or journeying through the wilderness using Survival.
This system also adds two new background skills: Artistry and Lore. A counterpart to Craft and Perform, Artistry is about developing a creative work that isn't necessarily an object or a discrete performance. This skill can be used to write plays, musical compositions, poems, and all sorts of other works. Lore, on the other hand, functions like an especially specific Knowledge skill. A character might know Lore (elven history) without being trained more generally in Knowledge (history), or could be well versed in Lore (artistic masterpieces) without having ranks in Appraise, Artistry, or Craft.
For all additional info please see this link here:
http://www.d20pfsrd.com/skills/background-skills
