Mic Types
There are two commonly used studio microphone types, the dynamic and
the capacitor (also known as a condenser).
Dynamic mics work using a diaphragm and
voice coil, rather like a loudspeaker in reverse, and have the advantage
of being tough, modestly priced and they don't need a power source to
operate. Their disadvantages are that they don't reproduce high frequencies
as well as capacitor mics and they are not very sensitive, which means
you'll probably run into noise problems when recording quieter sounds
as you have to use more gain on the preamp or mixer. As a rule, dynamic
mics are used for live work, guitar and bass recording and for close
drum mic-ing. Kick drums usually require a special model designed to
handle the very low frequencies that kick drums produce - general purpose
models tend to have the low end filtered out to prevent rumble and to
reduce popping when used close up. Probably the best known dynamic mic
is the Shure SM58 vocal model
.
Capacitor mics were once very expensive, but now that there are lots
of cheaper far eastern models being imported, the competition has forced
just about everyone to ring their prices down, so now you can buy a reasonable
capacitor mic starting for around the same price as a good dynamic model.
Because they use a very light, thin diaphragm and no voice coil, capacitor
mics are very sensitive and response well to both high and low frequencies.
They are commonly used for studio vocals, acoustic instrument mic-ing
and drum overheads.
The disadvantage of the capacitor mic is that it needs power to operate and so must be connected to a mixer or preamp that can supply 48 Volt phantom power along a standard balanced mic cable. The exceptions to this rule are tube models, which have their own power supplies, and battery powered back-electret capacitor models, which are usually less sensitive than phantom powered mics.
Patterns
Mics can be designed to pick up sounds mainly from one direction (cardioid),
from all directions (omni) or from
both the back and front but not from the sides (figure-of-eight). 
Dynamic mics invariably offer fixed patterns, usually cardioid, whereas some capacitor models can be switched between patterns. In the project studio, the cardioid mic is most useful as it reduces unwanted spill from other sources but omnis give a slightly more natural sound and so are preferred for classical recording and some acoustic music recording.
Up The Tubes
There's a lot of hype talked about tubes, but a well-designed tube mic
does sound good, partly because of the 'kind' way they distort when faced
with high signal levels. The difference in sound between a tube mic and
a conventional solid-state model is quite subtle but the tube mic generally
has a more dense sound, almost as though the signal has been compressed
slightly. Tube mics are popular for vocal recordings because of their
flattering sound but they cost around twice as much as their solid-state
counterparts.
The Price Is (always) Right
As with everything, you get what you pay for, but your money goes a lot
further now than it did a few years ago, especially if you're in the
market for a capacitor mic. Large diaphragm capacitor mics (the type
where you sing into the side) are popular for vocals as they tend to
have a slightly larger-than-life sound whereas the smaller stick-type
mics are used mainly for instrument recording because of their greater
accuracy. However, a budget large diaphragm capacitor mic with a fixed
cardioid pattern is a good all-round choice for the project studio
owner wishing to record vocals, acoustic guitars and suchlike. In my
experience, all but the cheapest imported capacitor mics work pretty
well but expect to spend upwards of $150 dollars for something worthwhile
as the very cheap models tend to have some shortcomings. Where possible,
compare mics, but don't get too hung up on the subject as most of the
models out there today are capable of great results if you use them
correctly.
TIP: Always record vocals using a mesh pop shield in front of the mic and try to arrange it so the area behind and to the sides of the singer is acoustically dead (improvise using sleeping bags or blankets if you have to). Most bad vocal sounds are down to either bad singers or a poor recording environment, not the choice of microphone.
