Contract work refers to working as a contractor indefinitely or temporarily for a company. Alot of job listings will say 6+ month contracting opportunity. After not getting a fellowship I became a contractor, the position was originally 6 months (however I was aware they could extend me), I was extended and worked 9 months total before finding a full time job.
You dont get benefits working as a contractor, however the contracting company you work for might offer services in exchange for part of your salary. My salary was 60,000 so I decided against that. It can be any job in industry, not just drug rep.