This is a bold (b) example and right next to it we have a strong emphasis (strong). Notice that strong + bold mixed looks similar but carries additional semantic meaning.
Here is an italic (i) word and an emphasis (em) example. Sometimes we combine them like italic + emphasis together.
Now let's look at text that appears crossed out:
strikethrough with s and
deleted with del.
You can also mix them: double strikethrough (s + del)
To highlight insertions or underlines: underlined with u, inserted with ins. A combination could be: underline + insertion together.
Subscript and superscript examples: Water is written as H2O using sub. The mathematical expression x2 + y3 uses sup. They can also be combined: CO2*.
Mixing several: This sentence has strong + emphasis, some bold + underline, and a formula like a2 + b3.