The cello is a member of the violin family (violin, viola, cello, bass viol). These four instruments (and other variants; violino piccolo, hardanger, baryton, viola d'amore, the Hutchins Octet, etc.) are topologically similar. Beginning at the top, the major components are as follows: Scroll, pegbox, pegs, nut, fingerboard, neck, body, strings, bridge, tailpiece, saddle, tailgut, endpin, and the soundpost (which is inside the body). Linings and corner blocks are structural parts and can be seen by looking through the "F" holes.
The scroll is more decorative than anything else. Its mass is a factor, but the shape is not. The scroll and neck are traditionally made from quartersawn maple. This is a very stable grain orientation and a yields an attractive grain pattern. Maple is quite strong and reasonably light.
The pegbox and scroll are an integral part of the neck. They have tapered holes to hold the pegs and a hollow area to allow the strings to wind around the pegs.
The pegs allow tensioning the strings. They are precisely tapered to allow adjustment of their friction for easy tuning but minimal slippage. Pegs are traditionally made from ebony, boxwood, or rosewood. Cheaper instruments may use dyed pearwood or other very hard woods. Occasionally, "patent" tuning pegs suchg as Caspari pegs are found and, even less commonly, geared machine tuners. If the pegs should slip, a light application of chalk or a peg compound will often fix the problem. If they stick, a tiny bit of beeswax may help. Peg compound can be purchased at any violin shop. It is a compressed mixture of wax and some very mild abrasive in a convenient stick. You can do great damage by using a do-it-yourself approach to repairs. Anything serious should be referred to a competent violin shop. A cracked pegbox or damaged pegs are not always easy or cheap to fix.
The strings wrap around the pegs, pass over the nut, fingerboard and bridge, and are attached at the other end to the tailpiece. The height of the nut and bridge are adjusted so that the strings are just barely above the fingerboard at the nut, but the height increases towards the bridge so that the strings are about a quarter inch above the end of the fingerboard. If the string height at the nut is too low, the strings are prone to buzz. If too high, playability in the lower positions is poor. If the height at the bridge is low, the strings will buzz. If the bridge is high, the instrument will be unplayable in the thumb positions. It is best to have a competent cellist evaluate the setup of your instrument if you are a novice. There are nuances to setting the string height and bridge that many violin shops do not get right. Violin shops probably deal with violins twenty times more than they deal with cellos. It takes time to setup an instrument properly and an inexpensive student-grade cello will most surely be adjusted badly when it is purchased. It is well worth the expense to have it properly adjusted and a decent set of strings installed. The difference in sound quality and playability that can be achieved even on a cheap instrument is remarkable. It is unfortunately beyond the scope of this article to explain the intimate details.
Strings vary widely in price and quality. The strings supplied with cheap imported instruments cost $5 at most (2007 prices) and are not even fit to use for slicing cheese. Plan on spending closer to $100. Or, $150 and more for an advanced player. They do wear out. Don't expect to buy strings once a decade. Strings range from plain steel to exotic tungsten and titanium alloys. Whether you should get gut or nylon or Kevlar or steel or carbon fiber or other cores and windings depends on the kind of music, your skill and your instrument. Generally, an instrument for orchestral use will have heavier and stiffer strings. An instrument for chamber music will tend towards nylon and gut with silver. Soloists often opt for the more exotic materials to extract every bit of potential from their instrument. The difference between a $5 and a $50 set is immediately obvious to the player and listener. Beyond that, the tonal differences to the listener are more subtle but the difference in playability can still be huge. You will need to experiment and find what strings are best suited to your instrument and skill.
The fingerboard is traditionally ebony. Cheaper instruments may have rosewood or dyed pear or some other substitute. Occasionally some odd composite can be found, such as carbon fiber. The fingerboard is not flat in either direction. It curves from side to side to allow bowing each string individually. There is a slight hollow along the length to give more clearance when playing louder. The C and G strings have a flat area towards the bridge since they vibrate much more than the D and A and would otherwise buzz.
The bridge is special. It looks like maple, but isn't exactly. At least not the same variety that is used for the back and ribs. It is cut in a unique grain direction to yield the distinct spotted pattern found on the best bridges. As you bow the strings, they move from side to side. The top of the cello moves forward and back, like a drum. The bridge and soundpost transform the sideways string motion into a perpendicular motion that allows sound to be radiated. The height, width, thickness, curvature and stiffness of the bridge are all crucial to sound quality and playability. If the feet of your bridge (against the top) look like the sort of shoes Frankenstein wears, some ignorant brute has simply slapped an unshaped blank onto the instrument. It will hold the strings in the air, but no more. A properly cut bridge is graceful. A good bridge and strings will make a $50 instrument sound like one worth a thousand. A bad bridge will make the best instrument sound like it has been filled with glue.
Top: finest Italian spruce, cut in January in the dark of the moon from the south side of the tree, aged 200 years and shaped without a piece of sandpaper or a router within miles of it.
Back: Quartered maple.
Tailgut: genuine gut, not nylon.
Endpin: Ebony and metal.