ATIS actually stands for AUTOMATIC
TERMINAL INFORMATION SERVICE. ( Not meaning to step on Gary's toes here..

)
Here's the FAA's explanation plus an example of the type of transmissions. It was taken from the FAA's Pilot/Controller Glossary
The continuous broadcast of recorded noncontrol information in selected terminal areas.
Its purpose is to improve controller effectiveness and to relieve frequency congestion by
automating the repetitive transmission of essential but routine information; e.g.,
“Los Angeles information Alfa.
One three zero zero Coordinated Universal Time.
Weather, measured ceiling two thousand overcast,
visibility three, haze, smoke, temperature seven one,
dew point five seven, wind two five zero at five,
altimeter two niner niner six.
I-L-S Runway Two Five Left approach in use,
Runway Two Five Right closed,
advise you have Alfa.”
What isn't mentioned in the definition is that you must obtain this information PRIOR to entering the airport's controlled airspace. That's in VFR and IFR conditions.
( I assume IFR but since I'm not Instrument rated I don't have the experience and right now I'm too lazy to look it up in the FARS)
Hopefully this will make it somewhat more understandable.

An Aircraft Mechanic only needs two tools, Duct Tape and WD40.
If it moves and it's not supposed to - use the Duct Tape.
If it doesn't move and it's supposed to - use the WD40.
Intel(R) i5 CPU 750 @ 2.67GHz, P55M-UD4, GeForce GTX960 8.00 GB RAM, Windows 7 Ultimate (32 bit & 64 bit on separate HDs)