If you are an international student you will probably have to take the TOEFL exam. Some schools do not require TOEFL (MIT for example) but this is rare.
The TOEFL is an English language test - tests your English skills. It is computer based, and is adaptive. You don't need to take it if you are a resident of an native English speaker, or you studied in an English school. You should probably verify this with the universities. It costs around 150$, and you can take it several times. You send your scores to specific programs, and later on can send to additional schools for extra fees.
In Israel, there are some problems with testing availablity (you book the test date on-line, and there are no available dates) so you should take the test well in advance! You don't want to go to a different country to do the test (right?). The grade will count for 2 years. It takes about a month for the schools to receive the score reports. The customer services of ETS are not so good (to say the lease), so relieve yourself from this exam soon enough.
I suggest you take the GMAT first. Finish with the GMAT about 6 month to a year before application deadlines, so take the TOEFL when you are done with it (this is just my recommendation. You can manage to do them 3 month before the application deadline and even less). The TOEFL test is much easier than the GMAT, which contains most of the material of TOEFL, so it makes sense to take the GMAT first.
I did the CBT which is one format of the exam. Today, as far as know, the test is only available in iBT format, which I have heard is harder. The CBT test had a grade skale of 0-300, and the minimum requirement was 265.
Basically the CBT test contained 4 sections: Listening (you use headphones to listen to some lectures and conversations, and then answer some questions), Grammer, Reading, and an Essay. This is not like the GMAT - the focus here is purely on English vocabulary, grammer, and knowledge. The GMAT had much more focus on way of thinking, business logic, decision making, etc. You cannot write anything during the listening section!
In the iBT version there is a Speaking section.I have no idea how that works out.
Check out the TOEFL website: http://www.ets.org/toefl . You can download sample tests from the website and check your level.
In summary, this is an easier test than the GMAT. If you got around 700 in the GMAT, you should not have many problems scoring high in the TOEFL. You should probably spend 10-20 hours to study (mostly prepare yourself fot the format of the exam and types of questions). Do soem tests and you are done.