Problems of Star Formation Theory and Prospects of Submillimeter Observations

We consider current state of star formation theory and requirements to observations in millimeter and submillimeter ranges which are necessary for resolution of the most actual problems of the physics of star formation. Two key features of star-forming regions which define observational requirements to their studies, are relatively low energy of processes that take place there and smallness of corresponding spatial scales. This is especially true for the objects in the latest stages of ``pre-stellar'' evolution, that is, hot cores, hyper- and ultracompact HII regions, and protoplanetary disks. Angular resolution, sensitivity, and spectral coverage in existing projects of ground-based and space telescopes of submillimeter and millimeter range are not completely adequate to necessary requirements. To obtain detailed information on star-forming regions as well as on individual protostars it is necessary to employ a space-based interferometer.