If your AC is leaking water onto the floor it could be a result of several scenarios. Your AC unit contains a part, called the evaporator coil, whose function it is to cool the warm air blown over it. This is the source of the condensation and is totally normal. The moisture from the coil drips into the drain pan, down a white PVC pipe and into a drain.
The most common cause of the leaking water is a clogged condensation drain line. That PVC pipe can become clogged with dust, dirt, mold, etc. Remove the PVC pipe, take it outside, and blow the water house through it. That should provide enough force to clean it out.
Other possible causes is a rusted or cracked drain pan that may need to be replace, especially if your unit is over 10 years old. A dirty air filter can cause the leaking as well. If the air filter is clogged then it blocks airflow to the evaporator coil, causing it to freeze. When it freezes, then it eventually kicks the unit off and then melts. That melting all at once can overflow the drain pan. To avoid this becoming an issue make sure you are checking and replacing your air filter on a regular basis.
There are two more possibilities on why your AC is leaking water and these two are good reasons to call in an HVAC professional. First is a broken condensation pump. If your unit is in your basement then there is a pump that pushes the condensation from the unit to the outside. The other possible problem is low refrigerant. Low refrigerant will lower pressure in the AC system, causing the evaporator to freeze up and then melt. If you notice the air conditioner not cooling very well or if you hear a hissing noise then you very well may have a refrigerant leak.