SCADA is the acronym for Supervisory Control And Data Acquisition. It generally refers to industrial control systems. Thus, it is not a comprehensive control system but it rather operates as supervisory software superior to PLCs (programmable logic controllers) and other hardware devices.
HMI stands for Human–Machine Interface, i.e., it allows for interactions between human operators and machines.
Try the Reliance SCADA/HMI system on several example projects or download the installer of the trial version for free.