Typography is a wonderful art and has a long history. When humans turned from manual typesetting to machines, type writers and then computers, some compromises had to be made. One of these compromises was to use simple straight quote symbols for opening and closing the quote, rather than different quote symbols for opening and closing.
Note: which kind of quotes are used for opening and closing dependent on the language or and some convention. English uses upper quotes “…”, German opens with a lower quote: „…“, French uses ‘guillemets:’ «…», and Japanese uses hooks: 「…」
Quotation Marks have funny names in many languages. Germans call them “Gänsefüßchen,” or “little goose feet.”
See this Wikipedia article for more details.
macOS, iOS and other modern operating systems have a feature which replaces the simple or straight quote symbols with the typographic quotes. So, you type
"Hello!" and the quotes are automatically replaced with the proper (depending on localization) typographic quotes. This is called “smart quotes.”
This is pretty nice, but can be troublesome when dealing with Terminal and text editors. Scripting languages and shells always use straight quotes, and cannot deal with typographic quotes.
Now, if someone sends you a command or a script that uses quotes, and it goes through an app that replaces them with smart quotes, then bash and Terminal will fail miserably.
There is not much you can do, other than be aware of this and check pasted code carefully. There is something you can do to make this easier, though.
The default monospace font used in Terminal on macOS are ‘Menlo’ or ‘SF Mono,’ depending on the macOS version. Now these are fine typefaces, but their typographic quotes are not very curly at all, making them very hard to distinguish from the ‘dumb’ straight quotes that Terminal expects. The classic ‘Monaco’ typeface on the other hand has beautiful curly typographic quotes, making them very distinct from the the straight quote.
My favorite mono space typeface ‘Source Code Pro’ also has nice curly typographic quotes. I have built this table with many common monospace typefaces and their quotes.
Now this shouldn’t be your only criteria in choosing your Terminal font, but it may be something that helps avoid quote errors.