The device's memory capacity determines how much data it can hold. The bigger the memory, the more data it will be able to store.
Data is everything your phone needs to download and store in order for you to be able to consume it. Think of it as individual bits of information that take a certain amount of space on your device. It can be in the form of music, videos, images or text just to name a few.
Have a look at the data usage examples to help determine the amount of memory you’ll need.