DeckBuilding

A player can make their own deck from a collection of cards in their library.

A player can choose to add mostly low-cost cards to form 'aggressive' or 'aggro' decks. Or include some lower-cost control/counter-spells and some high-cost bombs. This is called a 'control' deck'.

Then there are mid-range decks that combine elements of both but typically have some over-arching synergies.

All of this terminology and mechanics are taken from Magic the Gathering.