Wiktionary
n. (plural of fieldnote English)
Wikipedia
Fieldnotes refer to qualitative notes recorded by scientists during or after their observation of a specific phenomenon they are studying. They are intended to be read as evidence that gives meaning and aids in the understanding of the phenomenon. Fieldnotes allow the researcher to access the subject and record what they observe in an unobtrusive manner.
One major disadvantage of taking fieldnotes is that they are recorded by an observer and are thus subject to (a) memory and (b) possibly, the conscious or unconscious bias of the observer. It is best to record fieldnotes immediately after leaving the site to avoid forgetting important details.
Fieldnotes are particularly valued in descriptive sciences such as ethnography, biology, geology, and archaeology, each of which have long traditions in this area.