Points of ellipsis are three periods (dots) in the middle or at the end of a sentence. Some word processors and writing tools, including Word, Scrivener, Google Docs, Pages, LibreOffice, and OpenOffice, will detect your using three dots and combine them into a single character.

Comma splices and run-on sentences are very common errors in prose. There are a lot of ways to explain them using terms like "coordinating conjunction" or "subordinating conjunction," but in this article we'll skip the jargon.