<details> & <summary>

works like an accordian - but without the need for script, supported by most major browsers (except IE & Edge)

To customize the title of <details> tag (of which would fallback to 'details' in most cases)

code

<details>
<summary>
What did the cat says when the mouse got away?
</summary>
You have got to be kitten me!
</details>

output

What did the cat says when the mouse got away?

You have got to be kitten me!