Elisp: Documentation Lookup
Look Up Function Doc String
The following function you will use often when you code elisp.
describe-function 【Ctrl+h f】, then type the function name. (if the function name is under cursor, you don't need to type the name, just hit Enter.)
In the help buffer, press Tab to move cursor to the link then press Enter to open it. Or use mouse to click on links.
Look Up Variable Doc String
describe-variable for doc string of variables.
Some words (symbols) in elisp source code are variables, not function.
For example, sentence-end-double-space is a variable.