This is the Suborder Heteroptera which is placed under the Order Hemiptera.
Heteropteras are closely related to Cicadas (Cicadomorpha), Planthoppers (Fulgoromorpha) and Aphids (Sternorrhyncha), all placed in the same Order.
Bugs are not, like Beetles or Butterflies, undergoing metamorphosis between a larval phase and an adult phase. Instead they have something called hemimetabolous or incomplete metamorphosis. When they hatch from the egg, they are already very similar the adult species, this is the first instar. To grow larger the nymphs have to shed their skin, after the last instar they change to the adult form, where they have reproductive organs and for the most also have wings.
There are over 40.000 Heteroptera species worldwide. According to the Statistics of Fauna Europaea there are 887 species in Austria (Subspecies not included).
The images here below only covers a small fraction of those.