alright, first of all it's not d20, but what do you care? the dm rolls the dice for you.
here are the basics:
shadowrun is set in the dystopian near future of 2060, it is a world where cyberpunk meets magic, where criminal subcultures rub shoulders with corporate elites, and where advenced technology competes with the power of spells and spirits. it is an age of high-tech low-lifes, shrouded in danger and mystery and driven by intrigue and adrenaline. those who play in it stand on the edge, always in the shadow of adventure.
in shadowrun, players take on the roles of shadowrunners. Many verieties of runners exist. of all races, genders and sized. each with their own area(s) of expertise.
shadowrunners commit crimes, unualy for money. when a corporation of other sponsor needs someone to do their dirty work, they look to the shadows. as the " deniable assets" runners make advantageous - and expendable - tools.
runners usualy operate in teams. a team can be any combination of character types, depending on what the players want to do. the team should have a plausible reason for working togather, such as being old friends or cellmates, having the same interests, or even being forced togather by circumstance.
runners have contacts, who represent other potentially useful people they know. some of these will be other underworld types, like a gang member or a hitman. others may be ordinary people, useful for information of for "special arrangements" - for example, the corporate secretary who lets you know when the wiz reaserch scientist you're supposed to kidnap will be leaving the building.
the most important contact for shadowrunners is the fixer. a fixer acts as a middleman and can usually help the runners find gear, other contacts or work - all for free, of course. a corporation or other employer that needs shadowrunners sends someone to a fixer to ask for recommendations. if a team of runners has a good reputation and meets the job requirments, a meeting is arranged to duscuss details and haggle over payment. because such matters are highly sensitive, anonymity is par for the course, and employers of this type are known simply as "mr. jonson"
mr. jonson may not always be a corporate representative. the world of shadowrun is rich and complex, with many people and groups who may need to hire runners to accomplish certain goals. a criminal syndicate may hire runners to strike at rivals, a mage may hire them to acquire certain rare materials for magic use, or Joe Neighbor may need to find the terrorists who kidnapped his wife. regarless of the sponsor, if a job involves doing something dangerous and potentially illegal, it's a shadowrun.
runners accomplish their tasks by working the streets for info, calling in favors and markers from friends and contacts in the shadows. they take whatever action their job requires: surveillance, theft, breaking and entering, even murder.
runners do these things because they are survivors, many of them grew up committing crimes to get by, or perhaps they obtained special training somewhere and want to put it to use.
basic runner types:
DECKERS are skilled at computer programming and maneuvering through the datastreams of the virtual-reality telecommunications grid knows at the Matrix. they use special costume build computers knows as cyberdecks that allow them to project their minds directly into the matrix's complex, 3d reality. by illegaly logging on to the matrix, deckers can run search routines, tap phone calls and break into system hosts to retrieve data.
MAGES are one type of magician character, known for using thaumaturgical abilities in a scientific manner. to mages, magic is about knowledge and structure. mages cast spells, prcieve and project astrally, and conjure elemental spirits.
ADEPTS, the moden-day ninja and berserkers, use magic to enhance the body's abilities. adepts tend to be athletically oriented' with good stealth and combat skills (like monk in d&d)
RIGGERS have a piece of cyberware knows as a Vehicle Control Rig (VCR) installed into their bodies. it allows them to interface directly with suitably adapted vehicles, seeing through the vehicle's sensors and controlling it as they control their own bodies. riggers can use remote-control deck to do this from remote location, and they may even control several vehicles or drones at once in this manner.
SHAMANSare magicians who follow a totem spirit animal such as Coyote or Bear, and embody that totem's characteristics. to shamans' magic is attunement with the forces of nature. like mages, they cast spells and astrally project and percieve. they also conjure nature spirits and Spirits of Man.
STREET SAMURAI are physically enhanced combat monsters. with cyberware implands and combat skills, they attept to be the quickest, meanest and strongest killing machines on the streets. many of them cybernetically boost their reflexes to get an edge' or boost their strength so they can inflict more damage. many are also lethat with firearms' and almost all have a smartlink cyberware system installed for increasing precision in shooting.
the basic runner types are just the tip of the iceberg and are not emant to define a set of character classes. players can creat a dizzying variey of characters, for example a detective character who relies on charisma and skills as opposed to cyberware, or a covert operations specialist who has all the gear and cyberware neccessary to penetrate electronic defenses. the only limit is your imagination.
all that came from the SR3 rulebook, i hope they dont mind