Meditation involves focusing on your breath and constantly redirecting your attention back to your breath, trying to avoid distractions. This process requires a lot of prefrontal cortical activity, which is involved in attention. This high attentional load can improve your ability to pay attention and learn, and can enhance memory. However, it's important to note that these effects typically start to show after at least eight weeks of daily meditation, and it's presumed that you need to continue the meditation sessions to maintain these benefits.
At the neural level, when you sit or lie down and close your eyes during meditation, you shut down a major avenue of exteroception, or sensing things from outside of you. This shift in perception can have profound effects on how your brain and other neural circuits in your body function.
In terms of focus, continually bringing your focus back to a location just about an inch behind your forehead during meditation can increase your focus ability, not just during the meditation and afterward, but at other times as well. This 13-minute a day meditation practice is simple and effective, and can also have positive effects on mood and other aspects of mental health and performance.