Describe, Discuss and Explain

Can you please explain the differences the questions begin with these three words;'Describe...', 'Discuss...' and 'Explain...' ?

I am not quite certain how to answer those kinds of questions correctly.
Thank you

[Tdol]

Describe- detail the physical or other characterstics of something.
Discuss- talk about the good and point points of something
Explain- give information about how something works, the imapct it has or how it came into existence.