Greetings,,,
Dumb strings have all the lights, "nodes", change to the same color at the same time. Unlike older lights that just had one color. So, one main controller has only one group of signals sent to all the nodes. The R, G, and B signals are all the same at each node, and you don't have to have a separate intelligent controller at each node. Just the basic RGB levels.
Smart strings have an intelligent part, a separate controller, at each RGB node. So each is actually a separately controllable light, tied into a string with other separate lights. All these lights receive a signal from the main controller connected into the smart string. That controller is then able to turn all the lights on the string to the same color, or each light can do its own thing. Each just happens to be connected to other lights on a string to make it easy to hang lights up, and not have a thousand wires having to go to each separate light.
Prices are of course higher when you have extra parts on the smart strings, but as things go on, prices come down when things are done in large quantities, like everything else.
You have to have a little extra power to put to the microchips in the smart strings, but you gain finer control of the output.
Keith