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Why Hindus write Shubh and Labh with a Swastika?

I've seen this written at various places say shop entrances, home entrances and other places.

These terms are generally written besides Lord Ganesha's image. Not only this, it is also written on marriage invitations and Diwali greetings.

The terms are often associated with swastika symbol (well, most of the time).

So why they write the terms Shubh which means auspiciousness and Labh means Profit?

Shubh Labh with Swastika symbol

Image Credits : zns.india.com