What’s the difference between single double quotes? When and where should each be used?

Question

Tried a Google search but it is always someones interpretation through experience as opposed to hard and fast facts about its use. From what I can gather, double is used for a quote and single quotes used for quotes within it, though sometimes I see single quotes used outside of a double quote…

Edit: *Difference between double and single quotes – title

In: Other

Answer 1

Sometimes, single quotes are used to separate a discipline-specific term that may not be ubiquitous.

For example:
Redditors are expected to follow ‘Reddiquette’, lest they be smitten by the meme lord Cthulu himself.