At a high level, the only obvious difference between NTFS Junction Points and Symbolic Links is that Junctions are only able to be directories, while SymLinks are allowed to
Functionally, in windows, once created, there is no real difference. However, there are significant differences between them in what they can do. Junctions can be used only for the creation of links to folders, either on the same drive or different drives, but only if those drives are on the local system (you can not create a junction link to a folder over a network.) Symbolic links however, do not have the same restrictions. Symbolic links can be used to link to either files or folders and those files or folders can be located either on the same system (same drive or different drives) or to a network share and can make use of relative location symbolics ("\\system2\foldera\file.txt", "d:\foldera\file.txt", "\\system2\foldera", "d:\foldera" or "d:\foldera\folderb.." with the resulting link for the last 2 examples being the same location.) Relative location symbolics can be ".", "..", current drive relative function (if current drive is c:, then specifying "\tempa\folderb" results in a link to c:\tempa\folderb,) and current directory relative (if the current directory is d:\foldera\folderb, then specifying "d:file.txt" results in a link to d:\foldera\folderb\file.txt.)
To sum it up: Junctions Points are limited to folders on the local system only, while Symbolic Links can create links to folders or files accessible via a UNC path or on the local system with more versatility in how those locations are designated. Symbolic Links is basically a more versatile replacement for both Junction Points and Hard Links. Plus, Symbolic Links are compatible with Unix and Linux when creating a cross platform UNC pathed link.
Hopefully, this answers your question in a satisfactory manner. Edited to correct typographical errors.