What is suppossed to be in the definitions section of a research paper?

Definitions of terms is what you use in your work/ research. Depending on the subject there are specific terms and anagrams that are used in conjunction with the research. The reader needs to know what these mean. An example of this would be in education. I might use the term "ELD" but you may not know what this means, so it would be listed in my definitions of terms. By-the-way it means English Language Development and instead of writing it out over and over I can use the ELD in text after it is introduced, but it still needs to be listed in the definitions of terms.