The difference between a tornado watch and a tornado warming is huge, but most people think they are synonymous with each other. A tornado watch means that a tornado is possible within your area and you should be prepared. Listen to the local news for updates on the approaching storm. Have a plan and know where to take shelter if the watch turns into a warning.
A tornado warning means that a tornado is occurring or will be shortly. Take shelter immediately in a safe space such as a basement or storm cellar. If you have a phone or radio available, listen to your local news for updates and when it is safe to leave your safe space.