What is the difference between 2-1-1, 3-1-1 and 4-1-1?

An N11 code or N11 number is a special abbreviated dialing telephone number within the North American Numbering Plan, which allows access to special services. Usage is generally assigned as follows:2-1-1: Community services
3-1-1: Municipal government services, non-emergency
4-1-1: Directory assistance
5-1-1: Traffic information or police non-emergency services
6-1-1: Telephone company (telco) customer service and repair
7-1-1: TDD relay for the deaf
8-1-1: Underground public utility location
9-1-1: Emergency services

Generally, only 4-1-1 calls incur a toll. 9-1-1 access is mandated by law.

2-1-1 is the nationwide abbreviated dialing code for free access to health and human service agencies’ information. 3-1-1 is the nationwide abbreviated dialing code for non-emergency police and government agencies.

Calls to 2-1-1 are free and are routed by the local telephone company to a local or regional calling center approved by the Ohio Council of Information and Referral Providers (OCIRP). The 2-1-1 center's referral specialists question callers, access databases of resources available from private and public health and human service agencies, match the callers' needs to available resources and link or refer them directly to an agency or organization that can help. Calls to 3-1-1 work the same way, except calls are answered by the local municipality or governmental agency.

An excellent fact sheet can be found on the PUCO web site.