"used to be"和"used to do"都涉及到过去的行为或状态，但它们之间有一些关键的区别：

used to do

意思：表示过去常常做某事，但现在可能不再做了。

例句：

He used to go swimming in the lake near his house.

She used to smoke cigarettes, but now she has quit.

used to be

意思：表示过去是某种状态或身份，强调现在的状态或身份已经改变。

例句：

He used to be a teacher, but now he is a doctor.

This used to be a quiet neighborhood, but now it's quite busy.

总结：

"used to do"强调过去的行为或习惯，而现在可能不再持续。

"used to be"强调过去的状态或身份，而现在可能已经改变。

希望这些解释和例句能帮助你更好地理解这两个短语的用法和区别。