what is the significance of difference between two means?

Answer 1

I'm not entirely sure, because you question lacks context, but in statistics when we look at two groups of data and the two groups have significantly different means, then we have a pretty good idea that we are looking at two seperate populations, or processes -- that that something in a single process has changed so that the process is giving us different output than it used to.

So, in general, a mean tell you something about the population (or group of numbers) from which it is generated. Does it tell you enough to make a really good judgement? Not usually. Similarly, the min and max (smallest and largest numbers) tell you something as well -- range information. The median (especially when compared to the mean) can tell you something about spread, but the standard deviation tells you more. The mode can tell you something about frequency -- but usually not all that much. That's why an analysis of data usually includes all these things and more.

And having said all that, I'm still not sure I answered you question. But I do hope I helped at least a little.....