Proper pressure in your tires can greatly affect performance and the longevity of your wheels during use and in the field. For the proper operating range of the tire you choose, please refer to the tire manufacturer's website or the pressure range listed / stamped into the sidewall of the tire itself.
Additionally, the tire experts at Schwalbe have developed a nifty little tire pressure calculator for off-road MTB applications that can help you arrive at a starting point to ensure you that you are not running too little / too much pressure for your chosen terrain: https://www.schwalbe.com/de/pressureprof.html
Lastly, like the old saying goes, "too much of a good thing can be bad". Overly low pressures can cause a tire's carcass to wallow and roll during turning. And too low of pressure can cause premature rim damage. Pressures too high can cause a harsh ride and rims are only built to handle a certain amount of pressure - over inflation can cause rim failure and a crash.