1) what is bluetooth adapter?
Transceiver that communicate with your equipment using rs232 or usb or ... protocol on one side and to other BT devices using BT protocol
2) then, how to interface bluetooth adapter with microcontroller(i'm using PIC16F series?
depending from bt adapter you can connect it to your microcontroller using serial or usb connection. PIC16F does not have ability to perform USB HOST function so if you want to use PIC16F you have to use BT adapter with serial connection.
you can use some of the SENA adapters .. parani ESD110 for example like Bill told you .. and then connect
microcontroller <--serial-->parani<--BT wireless-->yourphone
3) can u ppl provide step by step connection?
this is not something that can be done in 3 lines of code and with few wires
4) Where can i find the bluetooth adapter in the indian market?
no idea, but check local distributors for SENA product, they have wide range of BT adapters.
5) is there any possibility of interfacing bluetooth module with microcontroller? If so, how?
depends on "what BT adater" to "what microcontroller"
if you have BT adapter with serial connection you can connect it using almost any microcontroller. You do not even need level shifter, just connect RX to TX and TX to RX and few status pins and you are ready to transmit/receive. Check the datasheet of ESD110/ESD210:
https://www.electro-tech-online.com/custompdfs/2009/01/ds_parani_esd.pdf
the other solution is to use some usb host capable microcontroller like
FTDI VNC1L-1A and then connect simple USB BT dongle to it.
In any case, you will have to program the microcontroller to recognise data sent by the phone, respond to phone's requests and decode the data sent by the phone.