The deck itself
Arcana — Latin for "secrets". The deck is split into Major Arcana (22 trump cards) and Minor Arcana (56 cards in four suits).
RWS — Rider-Waite-Smith. The most-taught deck, designed by A.E. Waite and illustrated by Pamela Colman Smith, published 1909. When tarot books say "the Tower," they usually mean the RWS Tower.
Pip cards — the numbered Minor Arcana cards (Ace through Ten), as opposed to court cards (Page, Knight, Queen, King).
Court cards — the four "people cards" in each suit: Page, Knight, Queen, King.
Suit — Wands, Cups, Swords, or Pentacles. Each suit is associated with an element and a domain of life.
The reading
Querent — the person who asks the question. Sometimes the reader is the querent (self-reading); sometimes it is a separate person.
Significator — a card chosen to represent the querent at the start of a reading, separate from the spread itself. Often a court card.
Spread — the specific layout of cards in a reading. Three-card spread, Celtic Cross, Horseshoe — each has a fixed number of positions with assigned meanings.
Position — one specific spot in a spread. In a Celtic Cross, the "Heart of the Matter" is position 1.
Reading — the act of laying out and interpreting cards in response to a question.
Pull — to draw a card. "Pull a card" usually means a one-card reading.
The cards themselves
Upright — a card that lands face-up in its normal orientation.
Reversed — a card that lands upside down. Reversals are read as the same energy turned inward, blocked, in excess, or releasing.
Keywords — the short summary of a card's meaning. Useful for memorising; insufficient as the whole reading.
Archetype — the universal pattern a card embodies. The Empress is the archetype of abundance and creative motherhood.
Correspondence — a card's traditional associations with elements, planets, zodiac signs, and Hebrew letters (per the Golden Dawn tradition).
Numerology — the symbolic meaning of a card's number. Aces = beginnings, Tens = completion, etc.
Reading concepts
Divination — using cards (or other tools) to gain insight into the future or hidden information. Some readers see tarot as divination; others as a reflection tool.
Shadow card — in some traditions, the card at the bottom of the deck after shuffling, read as the hidden or unconscious element of the reading.
Clarifier — an extra card drawn to clarify a confusing card in a reading. Use sparingly — too many clarifiers can muddy the original message.
Jumper — a card that falls out of the deck while shuffling. Some readers treat jumpers as significant; others reshuffle.
Trumps — older name for the Major Arcana. "The trumps" = the 22 Major cards.
Cleansing — the practice of resetting a deck's energy between readings, by smoke, moonlight, crystal, sorting, or intention.
Charging — energising a deck after cleansing, often by holding it or sleeping with it.
Open reading — a reading done without a specific question, to surface what is most alive right now.
Yes/no reading — a single-card pull for a binary question, where the card's built-in yes/no verdict is the answer.