Different mechanisms can start software when you sign in or while macOS is running. They should not all be treated as unwanted.
Login applications
These open for the user at sign-in. They can provide communication, sync, utilities, or a visible app window.
Background items and helpers
Helpers can update apps, synchronize data, support devices, maintain licenses, or provide menu-bar functions without opening a full window.
Launch agents and supported services
Launch items use macOS service definitions to run a process under specified conditions. Their labels and file names can be technical rather than user friendly.
Identify the owner
Use developer, identifier, path, signature, and parent application. Online Information & Comments can provide optional context, but verify important system decisions with the developer or administrator.
Decide safely
Disable an item first when you want to test startup behavior while keeping its app installed. Preserve backup, security, input-device, accessibility, and required work services.
An item that looks unfamiliar is not automatically malicious. Do not remove protected system entries or organization-managed services.