I get weird symbols in my output — what does it mean?

After I input the following:

data = Table[{3 + i + RandomReal[{-3, 7}], 
i + RandomReal[{-2, 5}]}, {i, 1, 20}];

model = LinearModelFit[data, x, x]

I got something weird:

(*   FittedModel[-1.65238+<<19>>x]     *)

Does anyone know what <<19>>x means?