Nowadays simply means at the present and current time, period, age or time. These days is usually administered to actions that has become a trend of some sorts in the current allocation of time.
"Nowadays, it is quite easy to make a fortune online."
Now and days is an inappropriate spelling of the word, nowadays which is a single word and not spread out into three words like the above. It currently is jargons with no specific and tangible meaning.
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