Ternary operator is a compact conditional assignment.

It serves to set a value of a variable depending on a boolean expression or a boolean variable.

a = b ? c : d;

The expression above is same as:

if ( b ) {
    a = c;
} else {
    a = d;
}

The a, c and d variables must be of the same data type (or type of c and d must be convertible to type of a using automatic conversion). The b variable is boolean.

b, c or d do not have to be variables. They may be constants or expressions. a has to be a variable.

For example, you can use a ternary operator to assign minimum of c and d into a in a compact way:

a = c < d ? c : d;