To generate the readers' interest in your research and to make them understand the significance of your work, it is essential to give background information about your study. The introduction of your research paper should provide the background of the study. While there are some essential bits of information that the background must include, there is no prescribed format for the manner in which it should be written. As you have correctly pointed out, a long and rambling background will make the readers lose interest. Therefore, you must ensure that the background is persuasive and engaging to the reader.
One of the main purposes of the background is to demonstrate your understanding of the field. You can do this by providing a critical review of the most relevant studies in your field that lead up to yours. Once you have discussed the contribution of other researchers in the field, you can identify gaps in understanding, that is, areas that have not been addressed in these studies. You could then explain how your study will address these important questions. In this way, you can put your research in context. You should then explain the significance of your research and how it will impact or advance the existing level of knowledge on the topic. Be careful not to digress from the topic of your research.
Related reading:
