Without search engine and without going into detail that is out of the scope, anarchy is a different path to a classless system. Said classless system is different enough from communism to warrant discussion but close enough for that discussion to be devolving into anarchy vs socialism most of the time to differentiate the path to that system.
Said path in anarchy is comprised of setting up collectives that start small, neighborhood small, and gradually evolve. Each collective shares almost everything between its members and there's no leadership or ranking across its members.
Anything deeper than that leads to a long discussion that is out of the scope of this thread and definitely out of the scope of the ELI5 the post I originally replied to needed or had the philosophical basis to understand possibly. I'm not saying one is better than the other, but they are quite different approaches to a similar goal, a classless society that money does not rule all.
And you keep using different names to describe them. As you should. Communism is not one thing and never was. But when people refer to base or true communism, the answer is just one.
It's how it was defined in the communist manifesto in 1848. You could say it's Marxism, but I dislike that naming since others played a big role on forming it as well, like Engels and others who based on Marx's mostly economic study added the philosophical and political angles.
Every theme or name change after the manifesto (that is not found in later revisions by the communist international) is attempts at adapting it with different angles and for different purposes and circumstances, aka NOT base or pure communism. Don't bundle everything in one basket and try to make sense, same way that bundling Putin's Russian form of Capitalism with US's imperialism and French Revolution's early capitalism together doesn't make sense either.
He asked for pure communism, I answered for that. If he asked about Trotsky, I'd focus more on the permanent revolution and the Fourth International. If he asked of Stalin, I'd talk about his socialism in one country theory