What does the phrase "two's complement integer" mean in Java's definition of primitive types?

Question

Java

We open the official Oracle documentation about primitive types and in the definitions of primitive types we meet the phrase signed two's complement integer. , for example here:

byte: The byte data type is an 8-bit signed two's complement integer. 

int: By default, the int data type is a 32-bit signed two's complement integer, which has a minimum value of -231 and a maximum value of 231-1.

What does this phrase signed two's complement integer mean. ?

Answer 1

https://en.wikipedia.org/wiki/%D0%94%D0%BE%D0%BF%D...
In particular, for byte this means that numbers take values ​​from -128 to 127, and not from 0 to 255 as it might seem.
Same for signed integer int

Answer 2

Good afternoon.
Mmm... well, you can google it, right?
https://en.wikipedia.org/wiki/Two%27s_complement
https://ru.wikipedia.org/wiki/%D0%94%D0%BE%D0%BF%D...
I think in Russian, yes and written in English quite informatively.