You can use chat to
・Clarify with the teacher to type the words you cannot hear or understand.
・Send or receive a URL of the teaching materials you would need.
If you want to send a chat message, right-click on your teacher’s profile picture and choose “Send a message.”
You can see your chat history by clicking on the teacher’s name on the left side of Skype application after you launch Skype.
If you don’t see your chat history, please try the following.
Go to Tools > Options > Privacy Setting and choose Forever on Keep History.
Go to Skype > Preferences > Privacy tab and choose Forever on Save Chat History.
Mouse over the top of your chat box and make the chat area bigger pressing the left mouse button.
You can also refer here.