From https://www.gnu.org/software/bash/manual/html_node/Special-Parameters.html,- (A hyphen.) Expands to the current option flags as specified upon invocation, by the set builtin command, or those set by the shell  itself (such as the -i option).I am not sure what it says. Can you give some examples for the meaning of a hyphen parameter?  
Meaning of a hyphen as a special parameter?
bash
You can echo $- to see the currently-enabled shell options:$ echo $-himBHThose are options you can provide with a - on shell invocation  bash -h -B  or later on using set.The flags are defined in the documentation for set. My options above are:-h  Locate and remember (hash) commands as they are looked up  for execution. This option is enabled by default.-m  Job control is enabled (see Job Control). All processes  run in a separate process group. When a background job  completes, the shell prints a line containing its exit status.-B  The shell will perform brace expansion (see Brace Expansion).  This option is on by default.-H  Enable ! style history substitution (see History  Interaction). This option is on by default for interactive shells.and i for an interactive shell.If I change the active options, say with set -x, I'll get a new value of $-:$ set -x +h$ echo $-imxBH