Is paint for airbrushing different from normal paint?

The only difference between normal paint and airbrush paint is that the airbrush paint has been thinned with a thinner and can go straight into the airbrush saving you the time and effort of having to thin the paint yourself.

If thinning the paint yourself, you want to reach milk-like consistency.

Please note that some acrylic paints may dry too fast when thinned with water and may clog the airbrush or create blobs of paint on the model. In that case, make sure you use the paint manufacturer's recommended thinner as it is likely to contain a retarding agent to delay drying.