If you review a document, it means you read it and examine it (and maybe have some ideas to improve it) - but you don't make any changes.
If you revise a document, it means you change the text to correct errors or make improvements.
When preparing for a test, it's a good idea to study the material again in order to refresh your memory. American English speakers say you are reviewing for the test. British English speakers say you are revising for the test.
ISO sensitivity is a measure of the cameras ability to capture light. Digital cameras convert the light that falls on the image sensor into electrical signals for processing. ISO sensitivity is raised by amplifying the signal. Doubling ISO sensitivity doubles the electrical signal, halving the amount of light that needs to fall on the image sensor to achieve optimal exposure.