:1 jumps to the first line, :$ jumps to the last line, :+ jumps to the next line, etc.
It seems to me that there is a default ex command which accepts a range and jumps to it: what's the name of this ex command?
Where can I find it in vim help? I guessed it might be in various.txt, but I can't find it.
This command has no name, but is simply the default behavior of the ex (and, notably, ed). Given a range, which may be one of the special sequences you mentioned, or a search, or even just a plain line number (e.g., :42), ex will jump to that spot in the file.
It does, however, have a place in the doc:
:help :[range]
As requested, an in-depth look at my help-searching process:
man ex: Always a good start. This took me to the vim man-page, which more or less points to the online helpman ed: Remembering that ex descends from ed, I thought I'd try here. I'm not sure if the behavior is documented there, but it was worth a shot:help ex led to :help Ex-mode, neither of which were helpful:help exusage: an interesting command to run:help range? Took me to a useful page, but not quite there:[range]command, so maybe :help [range]: Not quite, that's just above where we were:help :[range]: at long last.(This is slightly exaggerated: in reality, post-exusage I jumped straight to :help :[range] because that's the syntax of the command. It was a lucky guess.)
help exusage, and then that led me to a part of the index where i couldnt find it. So i thought well maybe ill try the range help (and I knew the syntax for the help doc bc it’s pretty standardized).
command_nameand add in the question how you would invoke the command and what it would output.:h cmdline-ranges. But that is obvious from how the ex-commands are acting that these are just ranges.