Quartz is a man-made stone that is usually 90% natural stone and 10% polymer resin. Since it is man-made the material is non-porous. Non-porous means that air, water, and other fluids are not able to flow through. That is why quartz does not need to be sealed.
Even though quartz is considered stain resistant it is still important to be cautious of spills. If a spill does occur, you want to clean up the mess right away. If the spill is left for a while and dried then a stain could occur.
To clean quartz countertops you want to use a microfiber cloth and mild detergent that is non-bleach and non-abrasive. Do not use an abrasive sponge because it can lead to scratches.
Quartz is not heat resistant or scratch resistant so it is important to use hot pads to avoid cracks and a cutting board to avoid scratches.