The top 3 elements to include on a poster are:
Like a research article or research paper, there are expectations that poster presentations include certain information, which may be organized in labeled sections if you choose.
Length: 2 or 3 sentences. Many conferences will include the poster essay or abstract you submitted when proposing to present within the conference program or booklet. This means that the full abstract doesn't usually need to be placed on the poster itself. Additionally, the full abstract would likely be too much text for the audience to read during a poster presentation session. You will want to include the basic information of your study such as the research questions you were hoping to answer, your hypotheses, and even a very basic overview of results.
Length: A few bullet points or sentences, and/or images, graphs, charts, infographics. This section tells people the "how" of your research or study. "How" did you set up your study to research your questions and test your hypothesis? Did you use a common research method or did you try a different approach? Methods also tell the audience who or what you studied to find answers. So if for example you distributed a survey, include a breakdown of your sample group with information on the sample size and group makeup. If you are presenting on a literature review, you may choose to skip including a detailed methods section since the audience will be familiar with that research method and won't need much of an explanation.
Length: Images, graphs, charts, infographics and likely a few bullet points or sentences. The results section is typically one of the largest. This section presents your data and the answers the data presented to you. Each research project is different, so you will have to consider your project and results to determine which results are significant, and which are less important and can be left off. It is extremely important to present the results without bias or omitting important information. Do not present a false impression of your research! Even if you consider your study/method to be a "failure" or all your hypotheses were wrong, it is ok! You learned something from the study you conducted, and that is what is important and what should be presented on the poster. Present results data honestly and fully.
Length: A few bullet points or sentences, or the discussion can be larger depending on the research project. This section provides the bigger-picture or overview interpretation for your results if the answers weren't clear from the data presented in the results section. It also provides an explanation for why the results are important (or not so important depending on the study) and what was learned from the research study. This section sometimes explains how the results could influence or inspire further research studies, or defines real-world applications that the current research would support. The discussion will sometimes clearly state whether or not the study aligns with earlier studies found within the academic literature.
Other than the title being at the top and center of your poster, there can be a lot of flexibility across academic disciplines for arranging the different sections of a poster. Depending on your specific discipline, however, the norms and expectations for poster arrangement and structure may be significant. These are most likely set by the traditions of discipline-specific societies or associations encountered within those areas of study. Asking a more established researcher within the discipline about the level of creativity acceptable in poster design might be a good idea if you are presenting at a professional conference for the first time without having ever attended. Additionally, if posters from previous conferences have been made publicly available online, reviewing these posters may provide further insight into that particular audience's expectations.