Low Altitude combat is a high-risk, high-reward style of fighting. It involves diving for the ground, and leveling out just above. Most dogfights occur around 500 ft. But more skilled pilots can maneuver under 200 with ease. Most pilots dive, level out, and do minimal maneuvers before climbing. Others tend to stay low, often trying to blend into the ground while running for objectives, such as a flag or base. In team death match and free for all, it can be helpful to attack from below. The Ho 229, being stealthy, is superb as it can't be seen on radar.
Fighting low to the ground can greatly benefit you. Whereas in higher altitudes it is just you and the enemy, flying low opens up a third variable. Flying between the buildings of the many towns, hills and airports to evade a pursuer is a worthwhile effort. As stated before, one can attack an unsuspecting plane from beneath, or play objectively while running a flag or attacking a base. Using the three tunnels on the Ardennes Offensive map can be beneficial.
Another recommendation: make sure you're using a maneuverable aircraft, with a Zero, you can easily go through buldings and such, lure your opponent into a village, however, they might know what you're doing and they'll pull up, by instinct, you'll do the same, but if they have a quite lethal plane in firepower and you're just recovering from the ascension, they'll be raining lead upon you quickly, but most of the Pilots don't do this feat and follow you through the buildings without considering their maneuverability.
Low altitude combat is tricky to master. If one intends to fly into the towns, an understanding of your planes maneuverability is needed. If it drifts to close to a building, one may overcompensate and slam into the other side. Also, one has to not only keep aware of a target in front and an enemy on your six, but the surrounding terrain. Losing focus could mean crashing, and losing a frag and a life because of it. Jets should mostly stay away from it, due to their high speed and low maneuverability.