Love is when you are as concerned about someone else's situation as you are about your own.

1. 本句，when you are as concerned about someone else's situation as you are about your own 是时间状语从句。is 是不及物动词，等于happens。

2. 状语部分是一个比较结构。第二个as 引导比较从句，省略部分为 concerned，但无法补齐，它由 as 充当。

3. you are as concerned about someone else's situation as you are about your own. 你关心别人的处境就像关心自己的处境一样。