Since idioms can be one of the biggest challenges in learning English, I thought I'd lend my expertise and explain some of them. If you come across one that doesn't make sense to you, please leave a comment, and I'll explain it to you. 

1. Show him/her the ropes:

This is one I've heard mostly in the corporate world when someone starts a new job. A more senior employee will be tasked to train the new employee. Show him/her the ropes basically means to show him/her how to do their job, but also to introduce the new employee to different departments that they might work with and the people they will likely interact with during the workday. The mentor showing the new employee around will also show him/her around the office and maybe also talk about the office culture to the new employee. So essentially, it just means to show the person around and explain how things are done. 

2. It's raining cats and dogs:

This is just an exaggerated expression to describe a heavy rainstorm. 

3. Starting a new chapter:

This is what someone says when they have ended something, and they're about to start a lifepath that is completely new. The concept being that your life is like a book, and this is a new chapter in your life story. 

4. Glass half full/ glass half empty:

This one has to do with your perspective on the world. If you see a half glass of water, is it half full or half empty? If you say that it's half full, then you are thought of as optimistic. If you say that it's half empty, then you are thought of as pessimistic. Sometimes, people will say that they're glass half full, and now you know what they mean by that. 

Have a great day everyone, and keep learning!