they seem to pertain to users who have an app

Yes without having a SE app (or an idea), why you need the key then?

Name The name of your application. If that is an idea you're going to implement, don't worry decide a name for that.

Description What your app will do part

Oauth domain Where SE want to redirect the user after authorization. you can give the home page itself if you want. It will contain an Object in response. You have to get particular details from it inorder to interact the user with SE.

Application website just give some link. A blank page is ok too.

Application icon if you want to show an icon to the app, upload it to imgur and add the link here.

###Note

You can edit some details after submitting at the url

https://stackapps.com/apps/oauth/edit/{{YOUR_APP_#}}

they seem to pertain to users who have an app

Yes without having a SE app (or an idea), why you need the key then?

Name The name of your application. If that is an idea you're going to implement, don't worry decide a name for that.

Description What your app will do part

Oauth domain Where SE want to redirect the user after authorization. you can give the home page itself if you want. It will contain an Object in response. You have to get particular details from it inorder to interact the user with SE.

Application website just give some link. A blank page is ok too.

Application icon if you want to show an icon to the app, upload it to imgur and add the link here.

Note

You can edit some details after submitting at the url

https://stackapps.com/apps/oauth/edit/{{YOUR_APP_#}}