Some corrections on what you know:
1) Modem Converts Analog to Digital then it sends digital signal to router, and assigns an IP connected to the WAN
IP packets don't care what medium it's traveling around in. Mentioning things like "analog to digital" and "digital signal" aren't needed unless you are building your own modem.
2) Router then converts this WAN so that it can be used as a LAN with switches so that multiple device can be connected to it. This is done via (TCP/IP)
A router forwards (i.e. copies) traffic between a WAN and a LAN. A switch lets multiple devices share one Ethernet port - in the case of most consumer routers, it's letting multiple devices share the "LAN" port.
Routers work using IP (Layer 3), switches work using Ethernet (layer 2)
2.1) An ISP only gives out one IP, therefore PORT is used to "divide" the IP so that it can be used internally.
NAT is used to "divide" the IP - and you can "divide" by telling NAT to forward traffic coming in on a specific port to a specific machine behind the NAT.
1) Where does NAT fit into all of this ? (Reading definitions of NAT
NAT allows multiple machines "behind" a router to share one public WAN-facing IP. NAT has to track each connection coming in and going out to keep track of who "has" what connection.
If you want machines behind the NAT to be accessible from the outside, you tell the NAT router that traffic on a specific port should be forwarded to a specific machine on the inside.
2) Where does bridging fit into all of this ? (Reading definitions
doesn't help too).
A bridge connects two or more nodes on the same network. Data is not modified when it passes through a bridge.
Your cable modem is a type of bridge, as is your switch and the 4 port switches often built into consumer level routers.
If you want to connect two or more nodes on different networks (you can think of "the Internet" as a separate network), you use a router, not a bridge. Routers forward traffic for networks behind them, and this means they "rewrite" the traffic since they are resending it for machines behind it.
3) Where does DHCP fit into all of these ?
DHCP is a way for a node to ask for an IP. A DHCP server keeps track of who has what IPs and makes sure no one gets duplicates.
Most consumer routers also have built-in DHCP servers. Machines behind them ask it for what is usually private, LAN IPs. Your router asks the ISP's DHCP server for a public, WAN IP in the same way.