Developers (Dev), Site Reliability Engineer (SRE), and Operations (Ops) are job types, while DevOps is a system. If we take a soccer analogy, Dev, SRE, and Ops correspond to positions like forward, midfield, and back, while DevOps is a formation like 4-3-3.

Dev

Also called Development Engineer, Software Engineer (SWE), Software Developer, or simply Developer (Dev). Their primary responsibility is to write code and implement software business logic. The logic could be fulfilling a grocery order, scheduling a cab to your place, etc. Developers mainly deal with the code.