[Polizeiposaune]

Depends on the processor architecture and its nomenclature.

Traps typically also result from exceptional conditions (like divide by zero or page fault).

An architecture may or may not provide non-trap paths for less-privileged code to invoke more-privileged subsystems (call gates, "syscall" instructions, etc.).

Traps typically need some way to preserve all userspace-accessible registers (otherwise resuming from a page fault is .. hard). Dedicated syscall instructions may only need to restore a subset of registers.

In some implementations, processors may discover that an instruction must trap after it starts irreversibly changing architecturally-visibile state; in cases like that, the processor needs to leave enough breadcrumbs for the OS to allow either a clean unwind or a resumption of the interrupted instruction. My understanding is that the original 68000 somewhat famously got this wrong.