Port 80 and 443 open on ATT provided router and question about ports

I am new to the computer networking world so bear with me please. Let me start with this, does a device need to have a port open to use a certain protocol, or does it need to be open if it plans to receive traffic using that protocol? For example, does port 443 need to be open on my computer for me to access a https website? Now, I connected my laptop to my phones hotspot and used nmap to port scan my router from the WAN side. It returned that Port 80 and port 443 were open. Is this a normal and secure setup? Why would those ports need to be open on the WAN side of my router?