Hi Renat,
Every mechanical object has its own natural frequencies of vibration, at each frequency it has different nature of shapes in 3D. Normally, the no. of modes is equal to the no. of degrees of freedom of the object. Since all 3D practical objects can be visualized to be composed of infinite no. of point objects, the no. of modes of vibration is infinite.
Also, for higher order modes, the effective displacement of the entire object gets reduced. In Coventorware, you can get as many mode shapes and frequencies of vibration as you want; it all depends on simulation time allowed. And the y axis shows some kind of normalized displacement. Refer to the design guides that came with your software package.