Modal analysis determines the vibration characteristics of a structure. The results of this analysis produces a mode shape and frequency. Note that the output modeshape is an eigenvector with the maximum value set to 1.0. Thus, the resulting deformations are scaled such that the largest deformation within the structure is 1.0 and is not representative of the scale of the deformations expected during actual vibrations.
Modal analysis can include constraints or not. Models run without constraints should have their first 6 vibration frequencies of essentially 0 since it’s a “free” mode. Partially constrained models will have less than 6 “free” modes.