Common terms (these are somewhat colloquial definitions):
(Health insurance) plan: The collection of benefits that you get from having health insurance
Benefits:
Provider: A doctor, nurse, therapist, or other health service
In-network: Means a provider whose services will be covered maximally as dictated by the health benefits of the plan. In-network providers contract with your health insurance
Out-of-network: A provider who does not contract with your health insurance. You will probably have to pay more to see an out-of-network provider
(More definitions will be forthcoming! If you have any questions, feel free to get in touch with someone in the care-committee channel!)