One of the last things people tend to think about when building a new PC is the airflow going through their case. Believe it or not, but this is a fundamental, and pretty crucial aspect of your build - it just happens to be less exciting than arranging your other specs like your CPU and GPU. If you're building a gaming PC, it might help you to know the differences between positive and negative pressure.
Intake vs Exhaust: How to tell the difference
Pro tip: Most PC fans have some handy arrows on them to show you which way the fan will spin, and which direction air will flow through it. Most of the time, you can also see a plastic frame on the back of a fan, which will indicate that air will flow out of that side.
