The data used by the microcontroller has a unit.
When the data is represented by the binary number, one digit is called a bit.
It may be handled by 4 bit, 8 bit, 16 bit, etc.
1024 bits are called 1K (Kilo) bits.
Please note that 1K is not 1000.
The nibble is a binary number of 4 digits and represents 1 nibble (4 bit) of data.
The byte is a binary number of 8 digits and represents 1 byte (8 bit) of data.
In addition, "Word" may be used.
There is no regulation that "1 word = the number of bits", and 1 word represents 1 data.
For example, 4 bit data is sometimes called 1 word in a 4 bit microcontroller, and 16 bit data is sometimes called 1 word in a 16 bit microcontroller.
Therefore, check in advance how many bits for 1 word are used in the microcontroller, and how to handle them.