There are 144 addressable RGB LEDs per meter on a white PCB, and each strip is sold in a 1 metre long length. Each strip can be easily cut, or can be 'daisy chained' with other strips in order to produce long chains of LEDs.
This flexible RGB LED strip uses the APA102 LED chips instead of the older WS2801 chips, LED strips that use these chips are often referred to by the name DotStar. This is a library created by Adafruit designed for use with this type of LED driver chip. The APA102 chips are easier to control and offer faster PWM rates for flicker free performance.