what is the difference between shiddah and jahr?

Question
What is the difference between shiddah and jahr?
Answer
Shiddah is imprisonment of the running of sound, so the sound does not run, whereas jahr involves imprisonment of the running of breath. Both are strong characteristics. 
The lessons on the characteristics are found at: http://www.abouttajweed.com/the-characteristics-of-the-arabic-letters/index.php