Comparing "li" and "cong"
Both 从 and 离 can be translated into english as „from“. But in chinese, their meanings are different. 从 refers to a „dynamic“ distance - distance which is changing. 离 on the opposite side expresses „static“ distance, which is not changing. Both can be used in defining distance or time. 从has more meanings than 离:
从
From (time) - 从….开始,从….起,从…..以来
从明天开始,我不抽烟了。
从有了女朋友以后,她不泡妞了。
From (place) - 从….到….,从…..向…..,
他从地上拿起来了一百块。
From (amount)
从学生到老师都放假了。
From (change)
他从最差的学生变成了最认真的学生。
离
From (distance)
我的学校离你家很远
From (time)
第一次世界大战离第二次世界大战不到50年。
现代汉语虚词俐释 (pp. 335)
实用对外汉语教学语法 (pp. 263)