Integers hold non-fractional numerical values. An "int" can have a value from -2,147,483,648 to 2,147,483,647.

int an_int; //this creates an int named 'an_int'
int another_int; //this creates another int.

an_int = 5; //this sets it to the value 5.
another_int = 3; //another_int is now equal to 3.

another_int = an_int; //another_int is now equal to 5.

an_int = 7; //an_int is now 7, but another_int is still 5.

The verge integer is 32 bit, here's a detailed run down of what that means:
In a 32 bit integer, there are 32 bits than can be either on or off
This is 2^32 combinations, or 4294967296
Binary numbers: 0 1 0 1 1.....0
Equivalent to: 2^0+2^1+2^2+2^3+2^4...-2^31
Which is: 1 + 2 + 4 + 8 + 16....-2147483648
Why is the last number (bit) negative?
So we can store all the negative numbers easily as well.
Then it is still just case of adding to bits to get the number.
Note that as 0 has to be stored as well, there is one less positive than negative
So in a 32 bit int, the number can be between -2^31 and 2^31-1
Alternatively in decimal from -2147483648 to 2147483647
Eg. The number 13 is stored as 8+4+1 or 1011000...0
The number -13 is stored as -2147483648 plus everything BUT 8+4 so 11001111...1
Note that the +1 is still on, as negative numbers stretch one lower than positives
Because the top bit is negative, in an overflow case (trying to store to large a number) you will 'wrap around' and get a negative number.