Posters have the same basic components as a manuscript (i.e. introduction, methods, results, conclusions, references, acknowledgements). They don't need to have an abstract because the whole poster can be though of as a visual abstract. It's a summary of your project that uses a combination of text and graphics. Not including an abstract will free up space that can be used for other content.
There is not one correct way to organize a poster but typically the sections are chunked and the poster is organized in columns. Below is a common format. The results will be the major component and there are typically 1 to 5 results sections depending on the project.
The benefit of this format is that it has logical flow. Posters are often read in the following direction.