There are different companies who offer these english exams so let me enumerate them to you and share whatever information I have learned about them from other people and references.
IELTS- International English Language Testing System
As mentioned the IELTS exam has four areas the listening, reading, writing and speaking subjects. The exam has 2 types of modules the Academic and the General Training Module. For Nurses, they usually take the Academic module. Academic module is usually taken by people who have intentions in studying abroad while the General Training Module are for those who are looking to migrate or skilled workers. The Academic Module carries more weight as compared to the General Training Module. I think the reason why nurses take the academic module is because at least if they have intentions of furthering their education later on abroad they would not need to take the exam again plus this is more readily available in the IELTS testing centers here in the Philippines. But it is up to you to decide which module suits your requirement.
The IELTS is usually a pen and paper exam though in other countries they are already starting to also make the exam computer based but so far here in the Philippines the exam is still pen and paper based.
The exam is taken for 2 days your listening, reading and writing test are taken in one day and the speaking test is scheduled on another day. The require score for nurses is an overall band score of 6.5 but for the speaking part if you intend on applying in the US you should get a band score of 7 and 6 for UK. You should not get a grade lower than 5.5 in listening and speaking areas.
Well thats about it... I would post more detailed information about this exam in my upcoming posts and well if you have questions feel free to post them up in the comments section.
Hope this information helps :D
Joan's Notes: Guys these information I presented to you are based on what I have read in different resources (Kaplan, Scott's English, Forums etc.) it would also help if you get verification from others. We aim to just at least give you guidelines and a little background. Have a good day everyone!