Informed consent is the act of making a participant in some academic
study aware of the nature of the study taking place. Though different institutions
have different requirements, some common elements
A statement of confidentiality where the participant is informed on whether their identifying information will be included with their responses. If yes, then the participant needs to know in what capacity, and if no, then how the primary investigator plans to keep that information secret. Remember, confidential is not the same thing as anonymous.
A description of the study's purpose, and how the data gleaned from the participant will be used eventually. Some common uses include instrument design and academic publishing. This should also include a blurb about what the participant can expect to happend during the course of the test.
A voluntary statement. It is currently considered unethical to force a participant to be involved in a study if they particularly would like not to. Therefore, each participant needs to be aware they can drop out of the study, without fear of reprisal.
If videotape of audiotape is used to capture data, then the participant needs to know the eventual disposition of those materials, and whether that media will be used in presenting results.
Most institutions, especially universities have an Institutional Review Board that require informed consent from any researcher using human subjects.