if(condition)
  evaluated when condition is true
else
  evaluated otherwise (condition is false)


if(condition A)
  evaluated when condition A is true
if(condition B)
  evaluated when condition B is true regardless of condition A

if(condition A)
  evaluted when condition A is true
else if(condition B)
  evaluated when conditiion A is false AND condition B is true. Condition B is not even checked if A is true
else
  evaluated otherwise (conditions A and B are false)