What is the difference between them? I couldn't find any documentation on it. There used to be some which I found in a Google search, but it's now gone: https://developer.apple.com/library/ios/recipes/xcode_help-interface_builder/articles-storyboard/StoryboardSegue.html
The document has moved here it seems: https://help.apple.com/xcode/mac/8.0/#/dev564169bb1
Can't copy the icons here, but here are the descriptions:
Show: Present the content in the detail or master area depending on the content of the screen.
If the app is displaying a master and detail view, the content is pushed onto the detail area. If the app is only displaying the master or the detail, the content is pushed on top of the current view controller stack.
Show Detail: Present the content in the detail area.
If the app is displaying a master and detail view, the new content replaces the current detail. If the app is only displaying the master or the detail, the content replaces the top of the current view controller stack.
Present Modally: Present the content modally.
Present as Popover: Present the content as a popover anchored to an existing view.
Custom: Create your own behaviors by using a custom segue.
For those who prefer a bit more practical learning, select the segue in dock, open the attribute inspector and switch between different kinds of segues (dropdown "Kind"). This will reveal options specific for each of them: for example you can see that "present modally" allows you to choose a transition type etc.
Source: Stackoverflow.com