Pulsar is a fork of Atom, which was discontinued because almost everyone jumped ship to VSCode.
What does Pulsar do that is better than VSCode? All the features this article highlights are in VSCode too, and I can think of a bunch of features that Pulsar doesn't have (dev containers are a big one for me - they allow you to have different versions of the same software installed, depending what project you're working on right now... and you can work on/run both versions of the same software at the same time, on the same hardware... you can also emulate other CPU architectures in a dev container, some of the software I work with every day can't actually run natively on my hardware).