Toilets, Sinks, Showers, Tubs and Disposals - Toilet dripping into main drain

I may not have ther correct terminology, but when the toilet has not been flushed and is sitting undisturbed, I can hear water dripping into the main drain into the floor which then connects to the sewage line. How can this be stopped? Otherwise the toilet works fine, no trouble with flushing, I did recently adjust the chain to the flange in tank, to keep it from running which doesn't happen anymore. Could the flange be what is causing this? Toilet and mechanism is only approx 2 years old. Any help/advice appreciated. Thanks!

replacement of the flapper valve will most likely solve your problem

When the dripping is taking place, what is the level inside the tank? Is the water going into the center overflow tube? May just need adjustment.

what is the flapper valve and where is it located?:confused:

No water going into overflow tube, water level seems to be 1/4" below regular level. Other mechanism that attaches to float seems to be leaking? Not sure if this is normal....:(

There is only 2 ways for water to leave the tank and arrive in the bowl or piping and these are:

The fill valve not stopping at the right height and causing the water to overflow into the tube sticking up in the center of the tank

or

the flapper near the bottom of the tank that allows the water to enter the bowl when flushed. Depending on the brand of toilet you have it could be a flapper, ball, float, etc but if it is not sealing properly, it will allow water to leak by causing a dripping noises into the bowl/pipes.