A slide is a single page of a presentation. Collectively, a group of slides may be known as a slide deck.
In the latter part of the 20th century, a presentation slide was created on a transparency and viewed with an overhead projector.
In the digital age, a slide most commonly refers to a single page developed using a presentation program such as Microsoft PowerPoint or Apple Keynote. It is also possible to create them with a document markup language, for instance with the LaTeX class Beamer.
Lecture notes in slide format are referred to as lecture slides, frequently downloadable by students in .ppt or .pdf format.