Binoculars consist of a small ocular lens (eyepiece), a larger objective lens (ocular) and a prism, which is a block of glass that acts like a mirror. A 7×50 binocular means it has 7 times magnification and a 50mm diameter aperture to collect light for image clarity. The porro prism consisting of two right-angled prisms then reflect the light path 3 times and allows the body to be far shorter than a telescope. It also flips the image around so it doesn’t look upside-down As a general rule the higher the magnification the dimmer the image and narrower the field of view, and the larger the aperture the better the image resolution.
Astronomy binoculars usually weigh 800 grams or more and so you might need some stability support, such as a tripod. Waterproofing is not generally required but can be desirable if you live in an area of high humidity. Finally, in spite of shockproof claims binoculars are precise optical instruments and should always be treated with care.