All the above mentioned plants are carnivorous plants with different insect trapping mechanisms.
In venus fly trap, the leaf has sensory hairs on its surface. When an insect touches this sensory hair, it triggers the plant to close shut and the digestive juices are secreted. In pitcher plant, the leaf lamina is modified into a pitcher while the leaf tip is modified to form a lid. The nectar gland attracts the insects and traps them. Sundews have tentacles which release a sweet, sticky liquid. They enclose the insects when they land on it.