What is the difference between a fence and a fixer in Shadowrun? I've seen both terms used but am not really clear on the difference.
While both members of the shadow community, a fence and a fixer operate at different levels of it and have different roles.
A fence is a merchant dealing in black and grey market goods. They operate on the fringes of the shadow community - offering services to both members of the shadow community and the more garden-variety criminal. Depending on their specialization, they may even sell to normal people; in some environments, staples of life have to come in via less-than-legal channels. A fence can hook you up. They frequently but not always have corporate contacts, albeit unofficial. ("It fell off the back of a truck.")
In some cases a fixer operates as Mr. Johnson, in others he merely connects shadowrunners with one. No matter what, a fixer is embedded much more deeply in the shadow community. They deal in information, not merchandise, and that information is who's-who in the shadow community. A fixer knows the services an individual shadowrunner can provide, the kind of jobs they prefer to take, and the other runners in a local shadow community they can/will work with.
A significant difference is how shadowrunners interact with them. Generally, the shadowrunner approaches the fence. Unless you've made a whole lot of noise on a run, a fence isn't going to know what you've got to sell (or want to buy) until you tell him. By contrast, a fixer comes to you. The Johnson comes to him, and he reaches out to his network of shadowrunners to find the right team for the job.
The same person can operate as both a fixer and a fence. That's one person with two roles, it doesn't make the two roles into one.