Easiest way of picturing the whole bit vs byte thing, if you find it tricky to keep in mind, is to think in terms of letter and words.
Networks think in letters, to mean that internet providers work in bits, because the way that network transmission works is to send it one ‘bit’ at a time down the line.
Now the way your computer thinks is in words. That’s due to how memory is organised, for efficiency. It’s more efficient in terms of transferring data between the CPU and the memory to grab more than you need, as there’s a good chance that after you use the bit you need now, you’ll need the bit next to it afterwards. Sort of like how when you want to cook a meal you don’t go to the supermarket, buy one ingredient, drive home, prepare it and then drive back to the supermarket to buy the next ingredient.
Since your computer thinks in bytes, data is commonly referred to in terms of bytes when talking about ‘this is something you’re going to use on your computer’ stuff.