I review here the current ideas regarding the origin, evolution, and physical nature of hot diffuse gas in normal, starburst, interacting and merging galaxies, using recent X-ray observations with XMM-Newton and Chandra. Many types of diffuse X-ray structures, including winds, bubbles, halos, chimneys and fountains, can be formed in galaxies, and can enrich the intergalactic medium with mass, energy and metals. This has profound implications as regards galactic formation and evolution, and the enrichment and evolution of galaxy groups and clusters.