The Grandfather Paradox is when a person travels to a point in the past before they were born and kills one of their own ancestors, taking themselves out of the picture before they were able to travel back in time.
The Pogo Paradox is where interference designed to prevent an event actually triggers the same event.
The Predestination Paradox is like as follows: Say a man goes back in time and impregnates his great-great grandmother. The grandmother would thus give birth to one of the man's great grandparents, who would then give birth to one of his grandparents, who would then be able to give birth to one of his parents, and finally to the man himself. As a result, the man's very existence would be pre-determined by his traveling to the past, and therein lies the paradox.