Tarot is a western tradition Mystery, a tool used for accessing a deep and lesser understood part of the human mind. It helps gives words and meanings to the most deep seated feelings and thoughts and instincts which are hard to put into words. Tarot fetches these out to the light of day, bringing them to conscious awareness. Tarot is most commonly used for accessing guidance for oneself or others, for obtaining impersonal advice, to look at things differently, or, most controversially, for attempting forecasting (prediction).
Tarot is nothing to do with religion as such. It is what the reader think it is. The experience you will have in receiving a reading is a reflection of the skill, the outlook, life experience, attitudes of the reader. The common denominator here remains the traditional meanings given to the cards. There is no messing with these core meanings.
The oldest Tarot decks use Christian symbolism (Judgement, The Devil and so on) but as Tarot is thought to have originated in medieval Europe, this is hardly surprising. What is being talked to is not a spirit or an angel or the Devil. What is being communed with is one inmost self; the vastness of the human mind, or what Carl Jung called, 'the collective unconscious.' Read up what Jung had to say about the Tarot and how he thought it worked.
The Tarot itself is made up of a deck of 78 illustrated and numbered cards. There are many hundreds of different decks available, of different designs. The 78 cards include 22 Major Arcana (greater secrets, things of life changing significance) and 56 Minor Arcana cards (lesser secrets, still important, to do with all aspects of everyday life)
The reader thinks of a question then shuffles the cards upside down (blind) and draws cards at random, then turns them over for interpretation, trusting that the cards though drawn at random will still prove absolutely relevant as a reply. This is the wonder of Tarot, that they DO.
The reader of Tarot must learn the meanings associated with all these cards. It is like learning a code and uploading it into your mind. Then, in addition, the cards might inspire insights and visions which are nothing to do with the symbolism of the cards directly. What has happened here is that the cards have acted as a prompt for your deepest psychic understanding.
So anyone can learn to read Tarot. It is a STUDY but with a keen psychic talent or with long practice, or both, you can take your interpretations to new levels.
I hope this helps, but there is plenty of information of on-line. Mountains of it