Although we described the concept already, lets summarize here the three types of supports you see in structures and how they are shown:
Note that if in real life the beam had supports like that, in fixed support case, it would not move. In hinge supported case, it would only rotate around hinge, as there is nothing to prevent rotation. In roller support case, it would both rotate and also travel down with its own weight, as there is nothing to resist the moment or vertical movement (this roller here would only resist to a force in horizontal direction.
In the next post, we will give an example of solving reactions for a very simple structure, to illustrate the basic points we introduced so far, in this series.