Answer:
The three preternatural gifts are those which Adam and Eve received when they were first created by God in the Garden of Eden, i.e. - gift of immortality (freedom from death), gift of integrity (by which they did not suffer adverse temptations to sin, because their bodily emotions were perfectly controlled by their will), and the gift of infused knowledge (they did not have to study and learn about God and nature, but had a clear understanding given to them of all things, since they were to be the first teachers of all the rest of mankind).
These are called preternatural, because they are beyond (praeter means beyond) our nature as human beings. The gift of grace is called supernatural (super means above) because it is completely above all created being whatsoever.
These preternatural gifts were all lost when our first parents fell into sin.