The concept of the German Torpedo Boats in World War I was to execute torpedo attacks on bigger warships. While other nations like Britain started to increase the size and gun armament of their torpedo boats - or torpedo boat destroyers - and designed a ship that would later just be called "destroyer", the German Navy stayed with the idea of small crafts that were focus on their torpedo weapons.
Compared to the 1000t ships with 10,2 cm guns that were used in the Royal Navy at the outbreak of World War I, the biggest German torpedo boats were only about half the size and equipped with 8,8 cm guns as a secondary armamment to defend themselves against the British torpedo boat destroyers.
During the war, it got obvious that the artillery component of those boats had to be increased, therefore all torpedo boat classes laid down during wartime got more and larger guns - the climax were the large torpedo boats ("Große Torpedoboote") of the Design 1916 - with their four 15 cm guns and over 2000t in size they were the biggest and most powerful ships of their kind at the end of the war.
Its quite interesting that even those late designs officially never were called "destroyers", they were still labeled with the name "Torpedoboot".
Germany built over 300 torpedo boats until the end of World War I, and several of them were lost because of enemy actions. 50 of the most modern ones were interned in Scapa Flow and scuttled there in June of 1919, only a few of them were not sunk.
Of the 114 boats left in Germany, only 24 were allowed to be kept after the Treaty of Versailles, but most of the remaining boats were of such a bad condition that it was difficult to keep even 24 of them running. Most of those boats were later reconstructed and several of them were even used for auxiliary duties during World War II.