  Methanol masers which are traditionally divided into two classes provide
possibility to study important parts of the star forming regions: Class~II
masers trace vicinities of the massive YSOs while class~I masers are likely to
trace more distant parts of the outflows where newer stars can form. There are
many methanol transitions which produce observed masers. This allows to use
pumping analysis for estimation of the physical parameters in the maser
formation regions and its environment, for the study of their evolution.
Extensive surveys in different masing transitions allow to conclude on the
values of the temperatures, densities, dust properties, etc. in the bulk of
masing regions. Variability of the brightest masers is monitored during several
years. In some cases it is probably caused by the changes of the dust
temperature which follow variations in the brightness of the central YSO
reflecting the character of the accretion process. A unified catalogue of the
class II methanol masers consisting of more than 500 objects is compiled.
Analysis of the data shows that: physical conditions within the usual maser
source vary considerably; maser brightness is determined by parameters of some
distinguished part of the object - maser formation region; class II methanol
masers are formed not within the outflows but in the regions affected by their
propagation. It is shown that the "near" solutions for the kinematic distances
to the sources can be used for statistical analysis. The luminosity function of
the 6.7 GHz methanol masers is constructed. It is shown that improvement of the
sensitivity of surveys can increase number of detected maser sources
considerably.
