Microgravity is a correction for the term "zero gee" or zero gravity. The reason for the term is that a balance of accelerations only exists at one radius in the orbital plane. In a spacecraft, away from that radius (typically, the center of gravity radius), apparent gravity is not zero. For example, say you're in a circular orbit at 360 km (6731010 m), at the circular satellite speed of 7695.36 m/s. V*V/R at that radius, 8.797865 m/s^2, equals G/R^2, also 8.797865. But, say you're in a large cabin, 10 meters out from the orbital radius, at 6731020 m. At that point, V*V/R is 8.797852, and G/R^2 is 8.797839, a net acceleration of .000013 m/s^2, or 1.33 micro gees outward. An object initially placed at that point would move about 2.3 meters outward in 10 minutes (0.5*.000013*600*600). This is why it's called microgravity. In deep space, with no large gravitational attractions nearby, apparent gravity is essentially zero.