If you're doing extract brewing, i.e., kits, you can skip the mashing. Mashing is how we convert the starches in the malted grain to fermentable sugar. It's basically soaking/steeping the malted grain in hot water at a specific temperature for 30-90 minutes, then draining out the liquid ("wort," in brewer's parlance) to leave the grains and husks behind.
If you're brewing with extract then the mashing has already been done for you. The wort is condensed into a syrup or dried into a powder for you to reconstitute when you brew your beer. Many extract recipes will include the addition of small amount of specialty grains to add color and flavor. These are steeped in warm-hot water for about 30 minutes before you add your extract to continue brewing. This steeping is similar to, but not exactly the same as mashing since the goal is not to convert starches from those grains into fermentable sugar, but simply to pull flavors and color from them.