which is the biggest mosque in the world and which is the second one..?Is it in India..?

Answer 1

First is probably Mecca, and second Medina - therefore not India, sorry. However there seem to be various contenders, and maybe you can find others. The various websites hold information in different ways, especially about the calculation of capacity, and so direct comparison is not possible.

1. The Shah Faisal Mosque, Islamabad
Claimed capacity: 104,000
Details: the hall can accommodate 10,000 worshippers, the porticoes 24,000, the courtyard an additional 40,000, and an extra 30,000 in the outbuildings.
http://www.pilotguides.com/destination_guide/asia/pakistan/shah_faisal_mosque.php
http://www.islamicarchitecture.org/architecture/faisalmosque.html

2. The Mosque of Hassan II, Casablanca
Claimed capacity: 105,000 [NB the 3rd website linked here claims it is the 2nd largest.]
Details: It has space for 25,000 worshippers inside and another 80,000 outside. The 210-meter minaret is the tallest in the world.
http://www.ehabweb.net/morocco.html
http://architecture.about.com/library/blhassanIImosque.htm
http://www.postcolonialweb.org/morocco/arts/hassan/2.html

3. The Saddam Mosque (renamed the Al Rahman Mosque), Baghdad
Claimed capacity: nothing found
This mosque, which is planned to be completed in 2015, is a contender for third place "after those of Mecca and Medina."
http://www.globalsecurity.org/military/world/iraq/baghdad-mosques.htm

4. Al-Aqsa Mosque, Jerusalem
Claimed capacity: 400,000
It's also called Al-Haram El-Sharif (the Nobel Sanctuary). Details: 144,000 square meters, 35 acres, holds up to 400,000 worshippers at one time
http://www.atlastours.net/holyland/al_aqsa_mosque.html

5. Al-Masjid an-Nabawi (the Mosque of the Prophet), Medina
Claimed capacity: 500,000
Details: has a rectangular plan on two floors; the main prayer hall occupies the entire first floor; the mosque enclosure is 100 times bigger than the first mosque built by the Prophet and can accommodate more than half a million worshippers
http://en.wikipedia.org/wiki/Masjid_al-Nabawi

6. The Great Mosque, Mecca
Claimed capacity: 2,000,000
http://www.time.com/time/world/article/0,8599,101585,00.html
http://www.sacredsites.com/middle_east/saudi_arabia/mecca.html