The rules of the game are complicated and cards would look really silly if all of the cards had all of the rules of the effects they have printed on them.  Instead, the designers have come up with keywords to make things simpler, like Trample.  These lessons go in depth into this shorthand we use.

Keyword Actions

Everygreen Keyword Abilities

Ability Words

Keyword Abilities in Magic 2015 and Theros Block

Keyword Abilities in Magic Origins and Khans of Tarkir Block