Towards a classification of global integral constructions and functorial liftings using the small representations method

This is a survey article in which we discuss some recent approach toward the classification of global factorizable integrals, and constructions of Langlands functorial lifting using small representations. To do that we use the language of unipotent orbits and their relation to Fourier coefficients. We also introduce the dimension equation, and set our goal to classify all global integrals of a certain form which satisfies this equation.