Nowadays, the saying is frequently used to assure an understanding between two people in conversation. Next time you find yourself in a situation where details aren't convenient to say out loud, a simple "你懂的 (nǐ dǒng de)" conveys "you understand what I'm talking ab0ut."
Examples:
1.
Mike, nǐ zěnme hé Mary zài yì qǐ le?
Tom: Mike,你怎么和 Mary 在 一起了?
Mike, how come you are now with Mary?
Xiǎo diǎnr shēng, nǐ dǒng de…
Mike: 小 点儿 声, 你 懂 的… …
Keep it down, you know what's been going on…
2.
Zěnme le? Chóuméikǔliǎn de.
Lily: 怎么了? 愁眉苦脸 的。
What's wrong? Why such a long face?
Wǒ wàngjì zhǔnbèi lǎobǎn yào de wénjiàn le, jiéguǒ… … nǐ dǒng de.
Lucy: 我忘记 准备 老板 要 的 文件 了,结果… … 你 懂 的。
I forgot to prepare the documents for my boss, so now…well, you know what'll happen.