First, let you see the meaning of these two words:

Understand:

1 recognition; Acquaintance: I know him | Someone I know told me. 2 understand; Understanding: Through study, I realized this truth. ③ The human brain's reaction to the objective world. Including perceptual knowledge and rational knowledge. Social practice is the basis of the occurrence and development of cognition, the only criterion to test whether cognition is correct or not, and also the purpose of cognition.

Understand:

It is clear that only by looking down can we truly understand the wishes and demands of the masses. 2 query; Investigation: Go first ~ What's going on? Go for a while.

Both of the above explanations are from Xinhua Dictionary. Although they are all in general terms, I believe you can see some differences.

Let me give you an example: Example 1: Xiaoming knew Zhang Peng because a friend introduced him before.

Example 2: Xiaoming and Zhang Peng are good friends, so he knows Zhang Peng well.

I think you should know by now, and it's the same for yourself, so learn more about it.