Nice intro! :)

Worth noting that the right content for ALT attributes varies a lot based on context. One useful guide I've heard is to use ALT to provide whatever information a sighted user might get from the image, in full context.

So your examples might be:

<img src="./lady.png" alt="Ms Aniekan Inyang">
<img src="./dog.png" alt="a cute dog sitting on a couch next to a cushion with the Google logo">

...depending on whether the lady's identity is the key point; or if the article was about dogs in Google offices.

Purely decorative images should get an empty ALT, eg. a lot of websites have banner images that add no real content at all and can be ignored by everyone including disabled users:

<img src="./generic-stock-photo.jpg" alt="">

WebAIM have a great guide on this: webaim.org/techniques/alttext