There are many ways to Hub, sunilkunnoth.
I prefer writing here when I'm struck with an idea that fits HP's layout scheme. I'm also a reader. I've learned a few names of HP authors and enjoy seeing what they're writing and what they're saying on the forums.
I think most authors on HP write for leisure. They, like me, get a thrill from writing something and then putting it out there for strangers (and friends) to read.
But there are those who are writing on HP professionally. For them, this is a place to earn money by writing carefully crafted articles that answer definitive search engine queries.
The money I make from writing on HubPages is like a bonus. For others, the money they earn here is part of their income. This just goes to show how versatile the HubPages writing platform is and why so many writers use it!