As I said, the default for unknown files to open is Terminal, but that's only happening for these recovered files because all the real information about them, called metadata, has been lost. They probably don't have the extent for any application in the filename. But you can still try to open them in other applications, including Textedit, which may be able to show you want is actually in the file. Just don't save them back from those applications, as they will then be given the metadata for Textedit.
Just about every time you reboot you can end up with "recovered" files if you have applications open at the time of the shutdown/reboot. They are generally the work files from the various applications, like, for example, a Word document that is open but hasn't been saved in a while. The scratch copy of the document will be "recovered" because the space was allocated for the scratch copy but never saved to the directory proper. 99.9% of the time recovered files can be deleted safely, which is why they typically show in the Trash in the first place.