"lao" means "old" as in "old age" or "time" i.e. 老朋友 compared to 新朋友. 老朋友= old friends, while 新朋友 means "new friends". 旧 translates to "old/worn out" and is only used with non-living things. e.g.旧衬衫 - an old blouse This is probably the general difference. There may be more to it, but I did my best to explain it.

most of the time 老 refers to people while 旧 refers to things. 他很老。 这个东西很旧。

老不一定也只是指人哦。比如说，这是一辆老车，这是一家老厂，可以指以前的款式啊什么的意思，如果说这是一个旧车，绝对指的是这个车用过而且损害的程度。。

“老”一般用来形容有生命的物体，比如说“人、牛”等，“旧”用来形容没有生命的物体，比如说“书、桌子”等

‘老’一般指人，‘旧’一般指事物