FUors, EXors and the role of intermediate objects

The studies of FUors, EXors and other young eruptive stars are very important for the understanding of the earliest stages of pre-main-sequence evolution. We describe the current situation in this field. This is the short version of the review, presented in ``Non-stationary processes in the protoplanetary disks and their observational manifestations’’ conference, Crimean Astrophysical Observatory