There is no scientific evidence that proves horoscopes or the tarot deck has any factual basis. Although they can be captivating pastimes, there is no proven truth in either method of divination. The wording of many predictions is vague enough that the listener can draw his or her own conclusions.
Horoscopes use the relative positions of the planets, stars and other heavenly bodies to make a prediction about a particular person's life, such as "Now is the time to start a new venture." The person reading that prediction can interpret it any way he or she likes.
Tarot operates on a similar principle but with special decks of card — each with an image representing a concept. The arrangement of these cards is used to paint a possible picture of the issue at hand, but it operates on the power of the listener's psychology rather than any supernatural means and is therefore fallible.