SAT

SAT is an standardized test which is taken by students who wish to pursue their undergraduate education in USA.
Another such exam is the ACT.
Unlike JEE and other entrance exams in India, a good score in SAT doesn't guarantee admission in top American Universities.

Hi Sakshi, Early Action as the name suggests, you will be notified of the decisions in a month. Regular and non early action rounds take longer. Make sure you submit your entire application material if you apply under Early Action. Standford's early action has certain norms to be followed, you cannot apply to any other university under Early Action. Check the policy here http://admission.stanford.edu/application/decision_process/restrictive.html and also check the link given by Chetna S. You have time until Nov 1, all the best!

The right time to take SAT is when you are ready and fully prepared. Most students take SAT at least twice. Some take thrice. But the best time to take SAT is when you feel you are ready for it and can score well.
Most students take their first SAT after their 10th grade or in Middle of 11th grade. They take it again in the summer break between 11th and 12th grade.

Hi Anmol,
There are over 3000 colleges in US which accept SAT. Some of the top colleges are - Princeton, Harvard, Yale, Columbia, University of Rochester, Duke, Brown etc.
Most of these colleges provide scholarship depending upon you need. But they will only provide it if you are admitted. Some other bodies which provide 100% scholarships in India are - Dr. Manmohan Singh Scholarship for Cambridge, Next Genius Scholarships, Tata Scholarship for Cornell etc.

There is no restriction on who can take SAT. If you are planning to do Undergraduate degree in US, you should take SAT.
Another competitive exam for Undergraduate Admission in US is ACT.

Hi Juhi,
You can prepare for SAT and JEE together. Math asked in SAT is far easier than that in JEE.
But since there is no English related section in JEE, you will have to put in great efforts to prepare for SAT English/Verbal section.
Be aware that most students from India face troubles in SAT Verbal. Indian students perform pretty well in SAT math when compared to students from other countries (except China).

SAT is a competitive exam for undergraduate admission in US universities. Most universities in USA want that students should take this exam. There is another similar exam called ACT for US Universities.
Currently, SAT is out of 1600 marks.

Yes, you can go to US for undergraduate degree without SAT. There are many colleges in US which are SAT/ACT optional. This means that SAT or ACT is not a prerequisite to get admission in these colleges. One such college is Wheaton College in Norton Massachusetts, USA.

U need to give IELTS or TOEFL and score a bandwith of 7 to 9 and your score in 12th is also very crucial so please work hard from now on

It is an excellent career option provided you can afford it.