Tactics refers specifically to how a player uses his troops in battle. Strategy refers to a player's long-term goals, the types of troops the player uses, and the surrounding terrain. Nearly all strategy games involve the use of individual pieces known as 'units.' These units are divided into different types that are graphically distinct from one another, and often possess different strengths, weaknesses, and special abilities.
These games can be categorized based on whether they use strategy, tactics or some mix of the two, and whether they are real-time or turn-based. Challenges usually take the form of objectives that must be reached, or enemies that must be defeated. Strategy games require player to think and plan ahead in order to overcome challenges.