After you have set up the parameters and pressed the Run Simulation button, or if you instead have chosen to attach to a running simulation, the structure and coordinates of the molecule being simulated will be transferred to VMD, and then VMD will continually update the molecule with new coordinates as soon as they are calculated by the remote computer. At this point, the Sim form is used to control the state of the remote simulation, to kill or detach the job, and to control how some aspects of the simulation are displayed by VMD. Even if other simulations are connected to VMD, you can use the Remote form after this to set up and start other connections.
When a connection is made, the molecular structure read from the remote simulation is added to VMD's list of loaded molecules just as if it had been read from a file. As new coordinate timesteps are calculated by the simulation and sent to VMD, they are added to the internal animation list of that molecule, and can be played back using the Animation form and controls just as a `normal' molecule. In fact, you can read in new coordinate frames from PDB and DCD files and append them to the animation list of an on-line molecule just as with any other molecule. The main difference is that a molecule retrieved from a connected remote simulation will continue to get new data from that connection, until the connection is terminated. Such a molecule also has a few more options available for it, which are accessed through the Sim form (described next).