Hai Sofia,

GRE-Graduate Record Examination comprises of verbal, quantitative and analytical reasoning.

Verbal reasoning involves understanding meaning of sentence/word and selecting answers accordingly.

Quantitative reasoning involves using mathematical skills to solve problems with quantitative information.

Analytical writing involves providing responses with strong support/claim

The study material is available in the website https://www.ets.org/gre/revised_general/prepare/. You can prepare using these or you can buy books available for preparation. You can also go for coaching.

Now coming to TOEFL, it is to weigh your knowledge in English. It helps you to cope up with the academics the mode of teaching where is English. Institutes may seek either TOEFL or IELTS.

TOEFL involves testing of abilities in reading, listening, speaking, writing. So you have to read certain passages/paragraphs, listen to conversation/lecture and respond, speak about a topic which they tell you to do (it can be opinion expression, about you/your surrounding etc), write essay/opinion.

Test preparation material, preparation planner, sample question papers are available on the website https://www.ets.org/toefl/ibt/prepare/

You may also try books.