That‘s an arbitrary distinction, since encryption uses a key just like „code“ uses a dictionary. In a one time pad where your key is long, how is it different from a dictionary? And in a trivial cipher the key may still encode a dictionary.

Basically you are taking a subset of encryption using only substitution and calling that a code.

Yep! You've pretty much nailed it.

Cipher: exchanging letters to hide a message.

Code: exchanging words/phrases to hide a message.

Encryption: combining math + ciphers (sometimes code too!) to hide a message.

Codes are great for real people having fluent conversations, not so great for computers. We actually use "codes" all the time, but when they're used in large groups (and not a 'secret'), we call it "jargon."

"Push it to main, and I'll pull it in to my buggy branch to see if that works" will make almost no sense to anyone but a programmer who works with git and even then, only someone who's used git since everyone renamed the 'master' branch to 'main.'