What is the difference between UNION and UNION ALL

Create a Galactic Directory of people in the Star Wars universe using the Star Wars API (yeah, that's a thing. swapi). Design and implement a web application with an AngularJS (1.x) frontend and an ASP.NET Core backend, that meets the following requirements: ● Displays a paginated list of people, with some brief details for each. ● There should be a backend to provide functionality such as caching, aggregation, etc. ● Tolerant of errors due to API failure, network lag/timeout, etc. ● Allows a person to be selected, and displays more detailed information about them. ● Allows the person’s details to be modified, and saved. ○ The public API is read-only, so changes will need to be persisted within the application. ○ You can choose any method for persisting the data -- memory, filesystem, database, etc. ○ Bonus points if it’s SQL Server. ● In the future we might expand to include other entities (ships, planets, etc.), so make sure your design and implementation are extensible.