Application developer and software engineer according to swissICT careers both work in software development. They differ as follows:
An application developer primarily implements business applications (client/server, web, mobile applications) as a full-stack, frontend or backend developer. This can include an engineer who has studied computer science at a technical university such as ETH and works in a bank, insurance company or public administration, for example, as a software developer with the internal job title of software engineer and implements software for business applications there.
A software engineer implements hardware-related software, e.g. real-time, embedded, IoT software, e.g. for machines, robots, control and regulation technology, ATMs, etc. Often these are computer scientists who have studied computer science or electrical engineering at a technical university such as ETH.