A classical programmable (desktop) power supply allows users to set a voltage and a current limit, unlike fixed power supply (like a phone charger) which have fixed voltage and current limit.
Knobs, buttons and displays on the power supply panel are enough to say that the voltage and current are programmable. Some supplies have additional communication interfaces (USB, RS232, IEEE488, etc.), allowing a PC to take control from the panel and set the voltage and current limit. Obviously, a program needs to run on the PC to send the appropriate commands via the interface.
With the EE board, the HW panel is replaced by the WaveForms GUI, but the features are the same: you set a voltage (limit) and a current (limit). The actual relation between the voltage and current is given by the load; if resistive, then U=R*I. Either U or I reach the "programmed" limit, setting the actual behavior.
EE board and WaveForms offer more that simple "programmability":
ONCE: you have the equivalent of a HW interface (like RS232 or other) - this is the API set provided by the SDK. You can use that to control the voltage from a user application - similar to whatever PC program you would use to send RS232 commands.
SECOND: you can actually generate a waveform (with specific amplitude and frequency limitations). This feature is completely original; I did no see that on other power supplies. This in fact transforms the power supply into an AWG with huge current capabilities. To use that, you need to add power supplies as channels in the AWG instrument.