Severe Weather Watch vs. Warning: What's the Difference?
A watch is often issued several hours in advance of storms developing. It means the ingredients are expected to be in place later in the day for severe storms.
A warning means all the ingredients are in place, and a severe storm is occurring or imminent.
A watch means to be ready, while a warning means act now.
My favorite explanation when explaining the difference between a watch and a warning is to use tacos. A watch means all the ingredients are in place, and the ground beef is cooking. A warning means the taco is assembled, and the ingredients have all come together, aka the tornado/severe storm has formed.
The same idea is true with tornado watches and warnings.