Is there anyone in the industry telling me?
It has been unclear what happened during this period.
In general, a group of developers of Node.js were dissatisfied with the too conservative development progress under Joyent’s control, so fork gave io.js.
Then io.js version evolved relatively fast, and the number of versions 1.0, 2.0 and 3.0 increased rapidly.
At the same time, Joyent has adopted many means to communicate with developers, reorganized the development management mode of Node.js, and after gaining more general recognition, decided to merge the iojs and node.js codes again and synchronize the versions. In order to avoid confusion with io.js which already has 1.0-3.0, the following version numbers jump directly to 4.0.
This is roughly the same meaning, the specific time point and the development mode discussed can be searched by oneself, and relevant articles are introduced.
There should be no difference between io.js and node.js since Node.js 4.0.