Printing file.read() doesn't display file content

Question

I am not being able to understand why file.read() behaves differently when I save it in a variable. Here is the illustration:

with open("file.txt","r") as file:
    content=file.read()
    print(content)
    print("------")
    print(file.read())

And the output is:

a
b

------

So, the last line of the code is not printing anything out.

Anyone care to explain why?