“Adding jump state to command.” implies that position ((point)) that the added command is evaluated is added to jump state. In the other word, you can get back to (point) that you executed the command by using (better-jumper-jump-forward). I was trying to add “jump state” to (+spell/previous-error) and +spell/next-error. Note that +spell prefix means this command is provided by a Doom’s module. From a quick glance into the code, it is clear that — just like other Doom’s module — it implements branching condition to allow fallback behavior based on context such as current mode or available packages.

This is my summary of a more thoroughly explained evil guide, see here. Keymap Precendence in vanilla emacs overriding-terminal-local-map for terminal-specific key bind overriding-local-map keymap char property at point keymaps for the current character. Yasnippet keymaps are in this category. emulation-mode-map-alists. Apparently, its more multi-mode keymap management. I am not sure what this means, but if i have to guess it is used in modes that have its known key precedence or other complexity that its key binding system brings.