String duality suggests a fascinating juxtoposition of world-volume and target-space dynamics. This is particularly apparent in the $D$-brane description of stringy solitons that forms a major focus of this article (which is { \it not} intended to be a comprehensive review of this extensive subject). The article is divided into four sections: 1. The oligarchy of string world-sheets 2. $p$-branes and world-volumes 3. World-sheets for world-volumes 4. Boundary states, $D$-branes and space-time supersymmetry [This article is based on a talk presented at the CERN Workshop on String Duality (December, 1995) and the published version of a talk at the Buckow Symposium (September, 1995).]
Categories: hep-th