Introduction - If you have any usage issues, please Google them yourself
int y; // define y as an integer variable
y = 4; // r-value 4 evaluates to 4, which is then assigned to l-value y
y = 2 + 5; // r-value 2 + r-value 5 evaluates to r-value 7, which is then assigned to l-value y
int x; // define x as an integer variable
x = y; // l-value y evaluates to 7 (from before), which is then assigned to l-value x.
x = x; // l-value x evaluates to 7, which is then assigned to l-value x (useless!)
x = x + 1; // l-value x + r-value 1 evaluate to r-value 8, which is then assigned to l-value x.