Being green

Today I learned an English term. Someone said in an email that someone is "too green". Considering the context of the message, it did not make sense to me. What did caring about environment and nature have to do with her message? So, I searched for the term. When you say someone is too green, it means they are inexperienced, new to their job, not able to navigate and handle issues as good as an experienced person would. It all makes sense now.