Three categories of TCP/UDP port numbers

Today my topic is port number, three categories of port numbers, and some well-known port numbers we need to know for the National CompTIA Network+, Security+, and other tests
Port number is 16-bit values. 2^16, 2 to the 16th power is 65,536. The range of the port number is 0 to 65,535.

A port number defines a virtual port to a specific application or service running on a computer. A port number can define a virtual port to access a specific service on a server or a connection point on a client computer.
Playlists:

Ports, port #, & TCP/IP applications

https://www.youtube.com/watch?v=hc1yi_I1W4k&list=PLSNNzog5eydtfuhxfedXD3tRbt7c-Z5Se

Topology & cabling, & physical cabling structure:
https://www.youtube.com/watch?v=T5xQJkAamk&list=PLSNNzog5eydsZCgT6tlX7Zb4EU67_hxyA
Ethernet Basics:
https://www.youtube.com/watch?v=FkH_JIZbpU&list=PLSNNzog5eydvAxPHJiDybPomC1fFHf1KE
IPv4 Basics:
https://www.youtube.com/watch?v=vcArZIAmnYQ&list=PLSNNzog5eydt_plAtt3k_LYuIXrAS4aDZ
OSI Model and related:
https://www.youtube.com/watch?v=nFnLPGk8WjA&list=PLSNNzog5eydtQcezP4OrrLL5preHLLkGA .