In Maryland the local police chiefs issues CCW permits on a "may issue" basis. How strict the police are with issuing permits depends on the location. Generally it's extremely difficult to get a permit in areas near large cities, while in rural areas they are more relaxed. Permits, no matter where they are from, are excepted everywhere in the state.
Concealed carry is the ability to, legally carry a gun that is not plainly visible. This applies to carrying it on one's person, or inside their vehicle. While many states allow concealed carry of a firearm on one's person with a permit, most do not allow concealed carry in a vehicle, or have strict guidelines on how the gun must be stored.
Most states require the applicant be at least 21 to apply for a permit, along with other requirements unique from state to state. There is a fee invaulved in getting a CCW which varies widly from state to state. Some states honor the concealed carry permit of certain other states (see the Permits Honored section for a complete listing).