There’s many different ways to classify engineer experience. This is yet another

Levels of Software Engineering

Engineer I (Entry-level)

limited ability to complete tasks independently

Engineer II (experienced)

independently complete tasks for the most part

Engineer III (Senior)

complete tasks independently, and helps less experienced engineers in their work breaks down high level features into manageable chunks

Engineer IV (Staff/Principal)

determines high level features to be prioritized as per business value rarely writes software implementations