Since these binoculars will be used outdoors, possibly in rough terrain, it is important to look for a pair which is built to last and stand up to the odd fall or scrape. Unlike monoculars which is one small telescope and can only been seen through using one eye, binoculars is lke having two telescopes, one for each eye.
Binoculars provide three dimensional images that have more depth. While cleaning your binoculars, you should take care to see that no cleaning mark or scratch is left on the surface of the lens. The "10" refers to the magnification power of the binoculars, that is, objects viewed will appear to be 10 times closer than when they are viewed by the naked eye.
A 7 x 50 binocular shows a view magnified 7 times and it has objective lenses 50 mm wide. A good rule of thumb is, unless you are a private investigator or international spy, avoid buying a pair of binoculars with a magnification/zoom greater then 10x's. All things you see through a night binocular appear green, because you don't look directly at the objects but at their image on a phosphor screen.
After all, the precision and accuracy required for tactical movements are much higher. It is possible to get a nice pair of binoculars for a couple of hundred dollars so it is important to stick to your budget as it is equally possible to fall in love with a pair that cost a couple of thousand dollars. Many binoculars come with a front cover, which protects binoculars from the rays of the sun.
So, get a good pair of binoculars and enjoy the birding. You will also need to buy an atlas of the sky suited for astronomy, and a guide.