“the unsigned int can store a value much larger than a byte. ”
Since an analogRead returns always +, ‘unsigned’ is specified (int=0-65535, but plain ‘int’ will work too +- 32k).
type range
byte 0-255
char -128 to +127
int -32,768 to 32,767
unsigned int 0 to 65535
long -2,147,483,648 to 2,147,483,647
unsigned long 0 to 4,294,967,295