老师 is a respectful term and has more personal connection for a person who teaches the young while the other is a non-descript term for some professional courses teaching to adults, more like a lecturer or instructor. It does not conjure up the same images as a [school] teacher. An even more respectful term is 恩師

1、When we say the name of position: 教师&老师 are both ok, but 教师 is more formal （more like written Chinese) 老师（more like oral Chinese) 2、surname+老师 ok; surname + 教师 no eg.: A：请问你是做什么工作的？ B：我是一名教师/老师 A：哇，那我应该叫你刘老师。 （but we don`t say 刘教师）

1. You can call everyone who teaches you some knowledge a 老师， however a 教师 makes a living by teaching. 2. 老师 can be used as vocative expression like "早上好，王老师", You would never say "早上好，王教师" 3. One would call someone 老师 in order to show respect to those who are experienced, senior or older than oneself.

They are same and identical. Used interchangeable. But I generalize that 教师is one kind of occupation. When filling perfessional brank. And 老师 brings up one repectful feeling and reputation of someone that works as a teacher. At the other kind of saying. 老师 is addressed by pupils. 教师 is more high level teacher。他们有职业职称的老师but I just guess.

意思一样的，只是教师更正式一些，老师更生活化