"Can you please say what functionality to be tested?"
What would you like to know? If you provide specific questions we could answer them. Please give us an example of what you do not understand and then we will gladly help you.
Examples have been given on this page that are good examples. Read Nilesh's example about a house. Now, apply that to your tests. Basically, its general testing. You don't go into detail. Just check if the item works then move on for smoke tests.
A web page with a submit button may have a few images on it, some text and a form. Well, smoke test, just fill out the form with some information and hit submit. If the page submits without error, the test passes.
Same web page...Test all values for the form including but not limited to negative numbers, symbols, large amounts of text foreign languages, upper ascii characters, utf-8 characters, leave blank, etc. See if the images are aligned where they should be on the page ( which could also be in the smoke tests...depends on how much time you have ), read through all text for alignment, spelling, etc.
Do you see how the sanity testing pays attention to a lot more specific detail where the smoke test is quick and does not pay attention to very many minor, specific details?