With Modify|Copy To Repository you can copy the selected local file/directory to the repository. This operation can be used to create tags, although SmartSVN provides more convenient commands for this task (see Tags and Branches).
Repository is the repository of your local working copy, it can't be changed as copies can only be performed within the same repository. The local file/directory Copy Local will be copied to the project's Repository. The target directory is Into Directory. With Name will be the name (i.e. last component of the path) of the resulting file/directory. Because the copy is directly performed into the repository, you have to specify a Commit Message.
Use Externals Revisions to specify how to handle externals revisions . This option is only relevant for externals which have their revisions set to HEAD. By default, Leave as is will not modify any externals revisions. Choose Fix all to have all revisions set to their current values, as present in the working copy. Choose Fix except below to have all revisions set to their current values except externals pointing to the specified location or some subdirectory of this location.
Only when fixing externals you can make sure that later checkouts of the copied location will produce exactly the same working copy. Otherwise, externals which have been left at HEAD will continue to bring the latest revisions of that externals which are in general not equal to that at the time of creating the copy.