The ACT tests reading, grammar and usage, science reasoning, and math (Arithmetic, Geometry, Algebra 1 and 2, and limited Trigonometry). It also has an optional writing section.
The SAT tests reading, vocabulary, grammar and usage, writing (including an essay) and math (Arithmetic, Geometry, Algebra 1 and 2)
SAT SUBJECT TESTS
SAT II Subject Tests are offered to assess a student's mastery of a particular subject area. They are used as additional criteria by particularly selective colleges or to gain admittance into majors that require a specific background or skill set
ACT vs. SAT
Most colleges will accept either the ACT or the SAT. They are different tests and some students will do better on one or the other. Take a look at THIS COMPARISON CHART to learn the differences between the tests.
The TOEFL tests the ability of nonnative speakers of English to understand and use North American English.