You might not need to give any of these tests depending on where you're intending to apply.
IELTS/TOEFL are only needed if you intend to apply to a university in a country where one of the official languages is English (US, UK or Australia, for example) and your first language is not English i.e. the country where you have studied in high school does not treat English as a first language. Both are fairly equivalent, but TOEFL is easier compared to IELTS. IELTS is a UK/Australian qualification, while TOEFL is a US qualification. You need to give only one of the two. There are a few reported cases of Australian universities not accepting TOEFL, though, but I haven't found any university in UK with any such demands. For information of IELTS, go to
http://www.ielts.org and for TOEFL, go to
http://www.ets.org/toefl/ .
SAT is an American qualification. You may need it to get into all American universities (with marked deviance from this principle in the past few years), extra credit for UK/Australian/European universities or it is possible you can substitute your SAT Test scores with entry tests in your own country (if you are not American or European). Generally, SAT is given as:
SAT I only
SAT I + (SAT II x 1)
SAT I + (SAT II x 2)
SAT I + (SAT II x 3)
As far as I know, SAT I is a prerequisite for SAT II. SAT I is a Critical Reasoning Test, involving English and basic Math. SAT II are subject tests, including a variety of subjects. For more information, go to
http://sat.collegeboard.com .
