Pseudoscience is a broad group of theories or assertions about the natural world that claim or appear to be scientific, but that are not accepted as scientific by the scientific community. Pseudoscience does not include most obsolete scientific or medical theories (see Category:Obsolete scientific theories), nor does it include every idea that currently lacks sufficient scientific evidence (e.g. String theory).
There is admittedly the demarcation problem, but this category comprises well-known topics that are generally considered pseudoscientific by the scientific community (such as astrology) and topics that have very few followers and are obviously pseudoscientific (such as the modern belief in a flat Earth). The pejorative term itself is contested by various groups for various reasons. Generally speaking, if an article belongs in this category, the article's lead will contain a well-sourced statement that the subject is considered pseudoscience. For people who advocate for these subjects, see Category:Advocates of pseudoscience.