Before television series, there was such a format as movie series, it appeared in the world immediately after the appearance of cinema. An example of this format is the film by French director Henri Pouctal «The Count of Monte Cristo», which consisted of 18 episodes. And here https://godsempires.com/why-ayaz-ahmed-left-kyy-l-en/ if you are interested, you can read about Ayaz Ahmed.
After the development of radio broadcasting in the 1930s, radio novellas appeared in the United States, they were short melodramas that were read on the air, and the denouement was postponed until the next time.
And only then there were TV series that were broadcast on TV. And so a TV series is a TV movie that may not immediately have a final point and it is usually divided into several episodes (always consisting of at least six episodes).
Generations of online cinemas
When the generation of online cinemas began, TV series turned into just series and now it was possible to interrupt the viewing and continue it later, with the advent of home cinemas, a lot has changed. One of the most famous online cinemas can be called Netflix, he was the very first to make series on his site. The first series exclusive to Netflix is «House of Cards», which was released on February 1, 2013, the series received good ratings and continued to be released until 2018.