A scientific poster is a popular method of presenting research findings succinctly at meetings and conferences. On a poster, which is usually designed on a computer using a programme like Microsoft Powerpoint, you summarize your research project using a mix of text and diagrams/images. You will then need to get your poster printed and take it to the meeting where it is to be presented.
A poster allows you to condense the aims, methods, results and conclusions of your research into a portable form of presentation. It also allows interested peers to understand your research in your absence, simply by reading through your poster. Presenting your research in the form of a poster at meetings or conferences can also boost your CV as it shows potential employers that you are motivated and creative.
Posters are usually made specifically for presentation at certain conferences or meetings after submitting an abstract of your research to the meeting organizers. Therefore you will know the audience you will be presenting to, which should give you an idea of the level of detail you should include.