In essence a pair of binoculars comprises two telescopes fastened together. The eyepiece lens magnifies this image. Binoculars are described using a pair of numbers, such as 7x50, 8x30, 10x50, etc. Since most astronomical objects are faint, choose binoculars with a large objective lens. A diameter of 50mm is good for most purposes.
Larger ones are heavier and harder to handle.
More magnification is not always better. As you become tired, it gets more and more difficult to keep a heavy or high-magnification pair of binoculars still enough to enjoy using them. For the average person, a magnification of seven times is probably best. If your hands are a bit stronger or more steady than most, you might consider ten times. Try out your binoculars before reaching for your wallet.