Tornado Watches and Warnings
As you recall, watches are issued by the NOAA Storm Prediction Center. A tornado watch means that the conditions are right for the potential development of tornadoes in a given area. This area can be cover part of a state to several states. A watch is used to alert the general public and emergency management officials to be prepared for severe weather.
Warnings are issued by the local National Weather Service Offices after severe weather has been observed at a location and could impact other locations. Warnings cover smaller areas and are more pinpoint with location information. When a warning is issued it means that actions need to be taken to protect life and property.
Source: National Weather Service