Returns is simply the percentage gain you make on an investment. For example if you invest Rs 100, and it becomes Rs 110, then you make a 10% gain.
But this alone means nothing. You need to know the time period. If the 10% gain is made over two years then the per year gain you make is slightly less than 5%, it is about 4.88% due to compounding.
However if you make the 10% gain in 6 months, then the fund house may just show 10% and the period against it.
Returns in long term investments are much better with direct plan mutual funds. They may be upto 40% more than regular mutual funds. Make sure you see the words direct plan in all your mutual fund schemes. Else switch to direct as early as possible.