Just what is <<pseudo:before>></<pseudo:before>> and is it useful to me?
info: That's the The outerHTML attribute of the ::before pseudo-element in DOM.
As that element does not have any "real" content in it (it has could have a CSS content:'' property)...
...you only get the outerHTML when you copy (& paste)
I don't think and AFAIK, can't be emulate/simulate this pseudo-element directly in DOM.
Now.. outerHTML is supported in all mayor browser at these days... and with Javascript you can can have an approach emu/simulating, but I don't know if that's really your question.
Edit: Screenshot added so you can find the reference of outerHTML directly in Chrome DevTools.
#question-header h1:before { content: 'Hi there! '; color: red;}