Pranab bro,
Here i am telling what exactly you want to know:
As Divik bro said, wifi extender used to connect one AP from other Router or device.
You should get wifi router at home. Which will solve your issue. No other expenses or investment.
Just tell us you want to continue with bsnl or any private players which is available in your location.
We will suggest wifi router accordingly. If you are going for private player the model will be included in installation charges and given by them.
With ethernet port you can connect internet to your PC. While with wifi router you can connect internet to your all wifi enabled devices. Like smart tv, mobile phones, tablets, ipod, ipad, google chromecast etc.
If you want to connect your broadband to your computer wirelessly then you need both wifi router and usb wifi adapter.
Cost for usb wifi adapter will be around 400-500.. while router will go upto 1200-1300 in online websites.
Connect the router to your computer via usb wifi adapter wirelessly and you are all set to enjoy the broadband without any yellow ethernet wire connected to computer.
This is how usb wifi adapter looks like:
Thanks