Yield to maturity (YTM) is the total returns (interest payments plus maturity amount or face value) expected on a fixed income security if the instrument is held till its maturity. In other words, YTM is the internal rate of return (IRR) of an instrument which is held till maturity and all the interest payments (coupons) are made as per schedule and re-invested at the same rate.
In short term funds, YTM depends on market yields (generally it is higher than overnight and liquid funds)