A/C Emergency Cut-off Cleaning and Maintenance
Ok, that appears to be the condensation drain pipe.  If you notice above the trap, you will likely have a removable cap.  I pour a small bit of bleach in that trap every year to prevent anything from growing and to keep it flowing, but you may need more or more often depending on your location.

The other key self maintenance step is to replace your filters regularly.  The thin blue fiberglass filters that are likely installed at the air handler will probably make it a year.  My friends refer to them as rock catchers since they hardly do anything to catch dust.  The thicker filters that you may have at your air returns should be changed more often, possibly monthly, depending on how much dust you have in your home.