Something conditional is dependent on other factors. You might receive a conditional offer of acceptance from a college, depending on your high school graduation and your maintaining passing grades.
For a clue to the meaning of conditional, look at an opposing term: unconditional surrender, which means someone surrenders and doesn't ask for anything in return. In a conditional surrender, someone will give up only if certain things happen. A conditional agreement is dependent on other factors: a company could make a conditional hire, meaning they'll hire you only if you finish your degree and take a blood test. When you see the word conditional, think "It depends."