To summarize the discussion up to this point, you may view the curl as an indication of the rotation or circulation of the
vector field calculated at any point. Zero curl indicates no rotation and the vector field can be generated by a scalar source
alone. A general vector field with nonzero curl may only be generated by a scalar source (the divergence of the field) and a
vector source (the curl of the field). Some vector fields may have zero divergence and nonzero curl. Thus, in this sense, the
curl of a vector field is also an indication of the source of the field, but this source is a vector source. In the context of fluid
flow, a curl is an indicator of nonuniform flow, whereas the divergence of the field only shows the scalar distribution of its
sources. However, you should be careful with the idea of rotation. Rotation in the field does not necessarily mean that the
field itself is circular; it only means that the field causes a circulation. The example of the stick thrown into the river given
above explains this point. The following examples also dwell on this and other physical points associated with the curl.