This is not meant to be a comprehensive list, since you could achieve that through Wikipedia, but instead just a list of flags that I think are noteworthy for understanding a given country/region.
China (PRC)
The big star represents the CCP, and then the four smaller stars represent the four social classes outlined by Mao during the revolution: workers, peasants, petit-bourgeoisie, and soldiers
Angola
I have nothing interesting to say about this one except that it looks dope as hell in this Séketxe music video:
The Merging of Two Yemens
| Pre-1990 | Post-1990 | 
|---|---|
| YAR: | |
| Merged to form Yemen | |
| PDRY: | 
Qatar and Bahrain
They look super similar, and yetâŠ
Qatar
Here the nine white triangles represent Qatarâs incorporation as the ninth âTrucial Stateâ via treaty with the UK in 1916. One of them represents Bahrain, and then the rest are the seven emirates which now make up the United Arab Emirates:
- Dubai
 - Abu Dhabi
 - Ajman
 - Fujairah
 - Sharjah
 - Ras al-Khaimah
 - Umm al-Quwain
 
Bahrain
It used to look way more like the Qatar flag, with eight white triangles instead of nine for some reason, but as of 2002 this was changed to five so that it could represent the Five Pillars of Islam.
Oman
The⊠I guess semi-interesting thing about this flag to me is that despite Oman being somewhat âcentralâ to the Arab world and despite being historically âlinkedâ to Yemen, it does not have a pan-Arab pattern:
Off-Center Circle Flags
Japanâs flag has the circle right in the center:
But in the flags of Bangladesh and Palau, the circle is slightly off-center. Hereâs Bangladesh:
And Palau:
Apparently this is because, when the flag is on a flagpole (since one side is attached while the other is flapping around), this offset actually allows the circle to seem more centered⊠Idk, I donât entirely get it.
Thailand vs. Costa Rica
Hereâs Thailand:
And Costa Rica:
Turns out, I think itâs a coincidence that they look so similar.
Cote dâIvoire vs. Ireland
Hereâs Cote dâIvoire:
And Ireland:
Puerto Rico and Cuba
Puerto Rico:
Cuba:
Burkina Faso
The⊠interesting thing about this one is that it was introduced by Thomas Sankara
and that the one it replaced (the flag of Upper Volta) looked identical to the German imperial flag, but⊠I think this was coincidental since it actually represented the Black, White, and Red Volta rivers which converge in Burkina Faso?