How can we get to know that which band represents which feature in image of sentinel 2?
can you explain your question a bit more? What do you mean by feature in this context?
This other post on the forum can help you
feature means land, water, settlement, vegetation, agriculture etc.
that is quite a basic question on remote sensing in general. In general, most bands (including their respective bandwidths) represent more than one surface characteristic, but there are some which are more suitable for certain features.
The post of MCG should provide a good start regarding band combinations.
Besides that I can recommend these tutorials:
You can load the CCI LandCover data, alongside to your S2 data and collocate both. But it has a very coarse resolution and will not fit well to the high resolution of S2.
To derive this information directly from S2 data, some scientific work is needed.