A solid mount. If the mount is not stable your image will jump about, particularly at high power. You should be able to move from one point in the sky to another quickly and smoothly. Fine motion controls are not necessary in most small scopes. Do not take any notice of magnification claims, it is aperture that counts.
Aperture is the diameter of the main mirror or lens of the scope.
All scopes are referred to by their aperture, from the smallest amateur scope to the largest professional scopes on mountaintops. Six inches or more in aperture. With a six inch it is possible to see any of the messier objects and beyond. This includes star clusters, nebulas, and dozens of galaxies. A scope of this size should also give good views of the planets.