What is WS2811 and WS2812b
Technically the WS2811 is an IC that can be purchased on the market all by itself, with no LEDs. When the 5050 LEDs were added everyone called them a WS2811 because of this. Along the way, the WS2812(b) came around which were more technically correct, as this indicated the IC + LEDs all in one package.
The WS2811 strip light is an external IC programmable LED strip too with 3 pins with positive, negative, and data line. Usually made to DC12v. Regular is 30 LEDs, 48 LEDs, and 60leds per meter.
WS2812B LED strip light is a built-in IC digital LED tape light with 3 pins including positive, negative, and data line. Voltage is DC5v input. Can be made to 30 pixels 60 pixels 74 pixels 96 pixels and 144 pixels per meter programmable strip light.