A more thorough explanation:

In the field of patents, a continuation refers to a type of patent application that is based on a previously filed application, but with some changes made to the scope of the claims. The new application maintains the original filing date of the previous application for the purposes of prior-art and interference, as long as it meets certain requirements.

For example, if a patent application is filed for a new type of widget, but the claims are rejected by the patent office, the inventor may file a continuation application with some changes to the claims. This new application would still be considered to have been filed on the same date as the original application, and would benefit from any prior-art that was disclosed in the original application.

Another example might be if an inventor files a patent application for a new type of software, but later realizes that there are additional features that could be added to the invention. Rather than filing a completely new application, the inventor could file a continuation application that builds on the original application.