A good airflow
A good airflow is defined by the outside air sucked in by the case fans through the air inlets, the fans of the components in the interior and the case fans blowing the air out of the system again.
A poor airflow leads to higher temperatures in the PC case. In addition to an impaired general performance, the consequences can also be emergency shutdown due to high temperature and in the worst case even damage to the hardware. Also, some fans may turn excessively fast, leading to a higher volume. A well thought-out airflow, on the other hand, leads to a quieter system by using the fans more specifically and with fewer revolutions per minute.
How to create a good airflow
Usually, a PC case is ventilated front to back and bottom to top. The case fans are the main tools for controlling the airflow. Since heat always rises and it is therefore cooler under the case than above the case, air vents without fans also support this way. Most cases are designed for exactly this kind of airflow, so it is considered a universal solution that almost always achieves at least good results.
After checking the temperature of the system, the position of the fans should be adjusted, in case individual components have a particularly high heat generation. For lower CPU temperatures, the front fans are mounted in a way that they are directed at the CPU cooler and the warm air is dissipated directly via the rear fan. For better GPU temperatures, on the other hand, you should aim the fans exactly into the area below the GPU, so that it pulls in more fresh air through its own fans.
If your case has a closed front, the front fans are much less effective. In this case, no pun intended, the use of top or bottom fans is an effective addition to the front fans then.
The power supply should be placed in a way that it is supplied with cooler outside air and not with the warm air from inside the case.
In order for the air to flow as freely as possible, a tidy interior is a very important factor. A good cable management with as few free-dangling cables as possible is therefore highly recommended, and not just for aesthetic reasons. You should also make sure that hard drives are not in the way of the air flow. The regular cleaning of the case interior ensures a constant cooling performance, because over time dust settles on the fan blades, cooling fins and fan filters above all things.