What does the idiom make heads or tails of it mean?

The idiom "make heads or tails of it" means to understand something. It implies that something is confusing or difficult to comprehend.

Here are some ways to use the idiom:

* "I couldn't make heads or tails of the instructions for assembling the furniture." (meaning the instructions were unclear)

* "The professor spoke so fast, I couldn't make heads or tails of what he was saying." (meaning the professor's speech was confusing)

* "I've tried to understand this painting, but I can't make heads or tails of it." (meaning the painting is difficult to interpret)

The idiom alludes to the fact that it's impossible to understand something if you can't distinguish its beginning (the head) from its end (the tail).