Lots of different ways to look at it - some people use it for fortune telling, others use it for meditation purposes at various levels of intensity, or to build a story, or, as GrimDamnFanjo says, to help you get insights into situations, your thought processes, and clarify a situation.
If you're just starting off, then the Rider-Waite deck is the one that's usually recommended - like many decks, it has 78 cards in total, 22 "Major Arcana" which are usually taken as representing the "Big" things in life - the archetypal mother, archetypal teacher, etc; 16 Court Cards (King, Queen, Knight, and Page), which are usually seen as representing people in your life and/or aspects of yourself (and sometimes situations), and 40 minor arcana, 1 to 10 in each of 4 suits (cups, coins/pentacles, wands/staves, and swords). Each suit corresponds to a suit in what we now use as the standard deck of cards (so cups corresponds to hearts and is usually about relationships, swords are usually taken as being equivalent to spades, and so on).
If you do decide to study it for long enough you'll also find it has links to astrology, numerology, and various other aspects of the "spiritual" and psychological.
There are hundreds of different decks out there to explore if you feel like it but the Rider-Waite is about the most common. The same goes for readings, from the "standard beginners" Celtic Cross (10 cards, starting with the current situation, and moving through to a probable outcome, depending on what you decide to do.
Enjoy the journey!