A keyword is a word or phrase that functions as shorthand for a longer piece of rules text. For example, Burrowing is a keyword that includes multiple related rules and abilities (e.g. can move between surface and underground locations, and can survive underground). Keywords are used to communicate concepts that require more text than what will fit on a card. You can find these longer explanations in the rulebook and the Codex. If a card gains multiple copies of a keyword ability, usually there is no benefit. For example, a Plumed Pegasus with Airborne and Power of Flight simply has Airborne. When the Power of Flight ends, the Pegasus will still have Airborne due to its printed ability. Sometimes, multiple copies of a keyword do provide a benefit, such as multiple Lance keywords, e.g. Thankless Squire.