Just starting out. Not sure I understand the difference between my instance being accessible via HTTPS and my instance being exposed to the internet.
Https is a secure protocol to access pages on a web server. It uses encryption to both secure the data and also authenticate the server you are connected to.
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To access HA remotely, you need to connect from outside you home network into your local network (aka LAN).
Very simply first your browser (or phone app) has to find your router. Then your router needs to allow your traffic onto your lan and direct it to your webserver (home assistant computer). One other complication is that your ISP can change your routers internet address for no reason.
You can register an internet domain name that when configured will find your router. Once you have a domain name, you can set up cryptographic keys for the secure https traffic (you don’t have to, but it is more secure, you really don’t want unencrypted traffic to you home system on the public Internet)
If you have a better router you can have the domain name route internally in you lan, but generally you don’t need to. ( Although some add ons like the secure connection)
But https and remote connections are two different concepts that complement each other.
This is very basic, but hope it helps.