Some of the questions answered below
Anatomy of the Bow
Outside of a set of new strings, or improving your own skills, upgrading your bow will probably have the most impact on the overall sound improvement of your musical performance. That makes it a crucial piece of equipment for almost all musicians.
Best suited for younger players because of its durability and cost, fiberglass is a great entry-level material for bows. As well, most fiberglass bows feature a plastic frog (the piece you hold) in order to further reduce costs.
Note: Most fiberglass bows are unable to be re-haired.
Another beginner material is brazilwood, regularly paired with an ebony frog. Lighter, and with a better response than fiberglass, brazilwood is generally considered quite fragile, so more care needs to be taken when using it.
Used generally in higher-quality bows, Pernambuco can beautifully hold a fixed curve, all while blending rigidity with flexibility. Most often used by more advanced performers, Pernambuco is often paired with an ebony frog, as well as leather grips and wire winding crafted of precious metal or faux whalebone.
Graphite-fiber (or carbon-fiber)
Equivalent in performance to brazilwood and Pernambuco, these bows are crafted using the same modern techniques found in high-tech sporting equipment. With a matrix of resin blended with reinforced fiber, these bows are extremely durable and quite flexible.
In order for your bow to be in playing condition, the horse hair must be tightened and rosin must be used. The first step is always tightening the horse hair though, or the rosin can't be applied correctly.
To tighten the horse hair of your bow you simple need to use the turn the adjusting screw clockwise. Remember though, between each performance the horse hair should be loosened in order to reduce unnecessary strain on your bow, but not so loose that it sags. As well, be careful not to overtighten the horse hair (by ensuring there is a visible curve in the stick) as this can cause serious damage to your bow.
Once the horse hair is tight enough, rosin is able to be applied. For beginners, becoming familiar with rosin is something that should happen early in your playing career. A rub that goes directly on the bow, rosin creates friction between the horse hair and the strings of your instrument in order to help them vibrate, which, in turn, produces the sound. The correct way to apply rosin is to add a single layer, then 3-4 complete length-wise passes more. As a musicians becomes familiar with their specific instrument, they'll be able to tell how much rosin to apply just by the sound the bow produces when used.