Torch

Torch is a type of block only found in Indev, Infdev, and Alpha. It is one of the few blocks that emit light, the others being lava, furnaces and fire. In addition, it adjusts its model in relation to the surrounding bricks, so that it looks like it's attached to any surrounding walls. Notch has said that torches will soon only be temporary sources of light, and that they will burn out over time. They are similar to redstone torches which are mainly used in logic gates.

Properties
Torches act as a full square, for the purpose of placing other objects or torches in the same area. Being a solid brick, this even prevents sand and gravel from falling down past a square with a torch on it, making it possible to build a roof completely out of these materials. If sand or gravel fall onto a torch they break, if they are placed directly above a torch they act as if they were on any other solid material. This allows them to be used as environmental triggers, such as airlocks. Torches also melt nearby snow and ice, making them useful to keep skylights from being snowed over and lakes from freezing in winter maps. Since monsters spawn in darkness, it is usual to use torches as light sources. However, some people use alternatives, such as fire and lava lighting.