What is difference between Pre-Signed Url and Signed Url

Question

I intend to private objects in a public bucket, thus restricting access to objects, not other objects in the bucket. And I want to set up CloudFront to serve content with Signed URLs. Now in AWS S3 documentation, I see two different terms, one is a Pre-signed URL to access a private object, and the other is a Signed URL which requires downloading a private key etc and doing something more.

What is the difference between Pre-Signed URLs and Signed URLs? Can I use PreSigned URLs with CloudFront?

C# Library has the method GetPreSignedURL, does it automatically download private keys etc and does signing or this GetPreSignedURL method is different than S3 URL Signing which requires setting up private keys and then signing URL?