If this is the case, the variable that is named immediately on the left of the equal sign will get the value on the right hand of the equal sign. The conditions after the IF clause usually compare one or several variables to numbers or other variables.
Parentheses help to structure the priority of conditions.
Usually, the variable to which a value is assigned IF the condition is true will be a new variable. However, if a variable is named that is already in the data set, the values of this variable will be replaced by those you just created. If two conditions are concatenated by AND, the whole expression is true only if both conditions are met. If two conditions are concatenated by OR, the whole expression is true if one of the conditions is met. AND, OR and NOT are called logical operators.