Starcraft 2 Strategies: The Defender's Advantage

New players to Starcraft 2 may not know the term "defender's advantage", or how it applies specifically to Starcraft 2.

In short, the defender's advantage is usually one of position or the ability to reinforce more quickly than the attacker.

Positional advantages:

• Vision / Sight
• Choke points near your base, either existing or made with buildings

Reinforcement Advantages:

• Combat will be close to your unit producing structures
• Structures are well protected behind a choke

What does this all mean?

It means that if your opponent builds mostly army with his resources, and you build your army and go attack him, by the time your forces get there, he'll have more stuff than you.  Thus, your only chance against his army happens if he decides to expand or tech rather than build attacking units.

And this, of course, is where scouting comes in...