The Tail Wheel flying is the flight of a plane with a tailwheel i.e. a conventional gear instead of the nosewheel (i.e., a tricycle gear). An endorsement is required from a certified flight instructor that the someone has undergone the requisite flight training. The endorsement certifies that the pilot is competent in normal and cross-wind takeoffs and landing, wheel landing and go-around procedures. Tailwheel flying is ideal for landing on back-country grass strips, which will allow easy access for back-country activities (such as camping, fishing, hiking, backpacking, etc.). Nose wheel aircraft cannot tolerate the unpaved landing strips; tailwheel aircraft is better suited for this purpose.
Low Altitude flying endorsement is the certification that a pilot is competent for flying the plane at really low elevations (500 ft or less, above the fround). Such endorsement is typically provided to air force pilots, but is also useful for aerial survey and agricultural flying. Low-altitude flying enables a plane to go undetected by a radar. Radar antennas, typically, are set for higher altitudes (5000-40000 ft.) and at lower altitudes, Earth's curvature provides shielding to the aircraft.
Multi-engine endorsement provides the certification in operation and handling of a multiple engine plane. The endorsement is provided for specific plane type, since each plane type has its unique features that need to be learnt. During the training, the pilots learn how to identify engine failure and which specific engine has failed and manage the failed engine. This endorsement enables a pilot to fly multi-engine planes, which can fly faster and higher as compared to single engine plane and also carry more passengers or cargo; and in many case, also offers more safety.
Formation flying is another name for precision flying. In formation flying, the pilot flies his plane relative to other planes in 3-dimensions (vertical, longitudinal and lateral). It is typically used for air shows and recreation and also may reduce the fuel consumption by reducing the drag on the planes. Military pilots use the formation flying for concentration firepower and mutual defense.
Pressurization endorsement enables a pilot to fly the aircraft at higher altitudes (above 25,000 ft), in a pressurized plane. The endorsement is required to ensure the safety of aircraft and the pilot in case of failure of pressurized systems, due to mechanical or human factors. The pilot gets certified in high-altitude aerodynamics and meteorology, use of supplemental oxygen, ensuring the respiration and prevention of asphyxia of the crew and passengers, etc. All the commercial, long-distance aircrafts require pressurization endorsement.
Hope this helps.