Bundle gerbes are a higher version of line bundles, we present nonabelian
bundle gerbes as a higher version of principal bundles. Connection, curving,
curvature and gauge transformations are studied both in a global coordinate
independent formalism and in local coordinates. These are the gauge fields
needed for the construction of Yang-Mills theories with 2-form gauge potential.Comment: 31 pages, final version, added one reference. To apper in CM