I'll give you a little bit of the technical details...
You only have one publicly visible IP address which your ISP assigns to your modem.
All internal devices are given standard 192.168.x.x or 10.10.x.x IP addresses that everyone in the world reuses within their own homes.
If you want, you can setup your router to take incoming connections requests to that one publicly available IP and forward it from the modem to whatever device you want. This is called port-forwarding. Incoming connection requests matching a particular pattern are forwarded to the device you choose. You could choose to forward incoming web connection requests to your camera by setting up the configuration in your router.
This is dangerous though, in that there are plenty of security holes in many camera devices and they have been hacked with rather alarming regularity.
A safer way is to invest the time in learning about VPNs. These VPNs punch a hole in your router to a single application called the VPN server which is hardened to a much higher confidence level (not 100% perfect but pretty darn close).
If you have a need for port forwarding, you need to make sure the device receiving connection request is confident to be safe from hacking. Cameras and NVRs are on the lower confidence level. I have
Blue Iris (and stunnel) running on a dedicated clean server that I need to make visible to the internet due to my business requirements but I believe my clean windows and only BI is safe enough for my risk/reward analysis.