Answer:
The Orion cloud is nearby, so we have a close-up view of star formation processes. We know the distance to Orion's star-forming regions, so we know how luminous objects are from simply measuring the brightness of the sources. We can see a number of stages in the formation process of stars and protoplanetary disks in the region. Orion is also close to the celestial equator so it can be observed from all the large observatories in the Northern and Southern Hemispheres.