An indication is a sign––it indicates, or suggests, some conclusion. The way you blush furiously when a certain someone talks to you is an indication that you have a crush on them.
An indication is like a clue, or a suggestion, but it's not proof. If someone is weaving all over the place when they walk, that could be an indication that they’re drunk. But then again, it could indicate an inner-ear infection that has ruined their balance. The verb, indicate, literally means to point out, by using your index finger. But indications don’t require actual fingers pointing to a cause.