What are stones and the difference between kidney stones and ureteral stones?

Normally, urine contains many dissolved substances. At times, some materials may become concentrated in the urine and form solid crystals. These crystals can lead to the development of stones when materials continue to build up around them, much as a pearl is formed in an oyster.
Stones formed in the kidney are called kidney stones.  Ureteral stone is a kidney stone that has left the kidney and moved down into the ureter.
The majority of stones contain calcium, with most of it being comprised of a material called calcium oxalate. Other types of stones include substances such as calcium phosphate, uric acid, cystine and struvite.
Stones form when there is an imbalance between certain chemical urinary components such as calcium, oxalate and phosphate.  These chemical components either promote crystallization while others inhibit it.
The most common stones contain calcium in combination with oxalate and/or phosphate.
A less common type of stone is caused by infection in the urinary tract. This type of stone is called a struvite or infection stone. Much less common are the pure uric acid stones. Much rarer is the hereditary type of stones called cystine stones and even more rare are those linked to other hereditary disorders.