Edit: i see now they're talking about private IP, but in case you want to learn about getting a static IP for other things...
Many ISPs will give you a dynamic (changing) IP rather than a static (unchanging) IP. Just check your IP once a week for a few weeks to see if it changes.
There are some services that get around this by checking your ip regularly and updating their records automatically. This is called a dynamic DNS provider (DDNS). I used to use "noip" but since then there are quite a few like cloudflare DDNS.
Beyond that you just would want to make sure your router or whatever device is assigning IPs on your network to give a static assignment to the server. Assigning IPs is handled by a DHCP server and it would usually be your router, but if you have a pihole you might be using that as a DHCP server instead.
Between DDNS and DHCP you can make sure both your external IP and internal IP are static.
CS50 is produced by Harvard and is opencourseware (free) that isn't going away.
What is changing is that Yale won't be offering CS50 courses going forward, seemingly due to funding issues.