A supplier is a company you would bill to that is not going on site to do work. Some examples of suppliers would be:
Hydro Provider
Natural Gas Provider
Water and Sewage
Waste and Recyling
Telecommunications
Software Subscriptions
Postage and Mail Services
Bank Fees
Insurance Providers
Professional Services
Janitorial Supplies Companys (Staples, Swish)
Laundry Equipment Leases
Vending Machine Contracts
Lightbulb and Maintenance Supply Vendors (Lowes, Homedepot)