Command; What you would type into your terminal to do something. For example cd is the command to change directories.
Path; A location on a computer, such as a folder (or folders), or file.
Macro; A combination of a defined command and path. For example you could write a macro to delete all pdf's (the command) in your downloads folder (the path).
Dispatch; To execute a macro
Ad-hoc; To do something as needed. For example you can register macros as needed, so you could say you are ad-hoc registering macros.
Namespace; The collection of valid names to dispatch with. ahd has it's own namespace meaning you can use names defined in other namespaces (like cd, user etc.). For example on your system your "global namespace" would be where commands like cd come from (on *nix this is ~/.bashrc and the PATH on windows).
Path Expansion (AKA globbing); To take a representation of a path (or paths) and expand it to a real (absolute) path, or set of absolute paths. For example ~/Desktop would expand to /Home/Desktop on *nix and %USERPROFILE%\Desktop on windows.