From the SOLIDWORKS help:
SOLIDWORKS Motion studies are graphical simulations of motion for assembly models. Motion simulation assumes all parts to be rigid during the simulation, meaning that during contacts, no deformations will take place.
Where to start?
To start a motion study in SOLIDWORKS you can click on “Motion Study 1” tab on the lower left corner of SOLIDWORKS user interface.
Make sure to click on “Expand Motion Manager” to display the SOLIDWORKS Motion Manager timeline view.
The first thing you need to do is to select the type of simulation you want to perform. There are 3 types of motion simulations in SOLIDWORKS including Animation, Basic Motion, and Motion Analysis.
Animation simulation is included in all the SOLIDWORKS Packages (Standard, Professional and Premium) and allows you to do quick animations for exploded views and rotating camera angles.
Basic Motion is also part of every package of SOLIDWORKS. You can use Basic Motion to show basic contacts between models, approximating the effects of motors, springs and gravity on assemblies. Basic Motion takes mass into account in calculating motion. Basic Motion computation is relatively fast, so you can use this for creating presentation-worthy approximate simulations of motion that account for mass, collisions, or gravity.
Just remember that in Basic Motion no forces are being calculated.
Motion Analysis is an advanced motion simulation. The add-in is available with SOLIDWORKS Premium, Simulation Standard, Simulation Professional or Simulation Premium. It can be used for accurately simulating and analyzing the effects of motion elements (including forces, springs, dampers, and friction) on an assembly. Motion Analysis uses computationally strong kinematic solvers, and accounts for material properties as well as mass and inertia in the computations. You can also use Motion Analysis to plot simulation results for further analysis.
To have access to Motion Analysis you need to activate the SOLIDWORKS Motion add-in from the Tools > Add-Ins menu.