Deadwood not only looks unpleasant it's damaging to your tree's health. Insects look to deadwood to build their homes and dampness promotes fungus and decay of the tree which leads to rotting.
Hanging deadwood is especially dangerous as it can break and fall causing damage to property or injury to others. The dead branches become very dry and can snap off in high winds and stormy weather. Deadwood removal is precautionary and prevents wood from flying through the air in a storm.
How to recognize Deadwood: Some branches have no leaves and other have leaves is a dead giveaway to spot deadwood branches. Dead leaves that cling while other branches have no leaves. Bark falling off of the tree and large cracks in the bark. One of the biggest telltale signs of deadwood is large fungus growing around the base of the tree and also on the bark.
Deadwood is when all the cells in the wood have died and will not come back to life which is different than dormancy. Dormant trees have buds that will grow in the spring, deadwood trees don't. Holes and cracks in the bark can also indicate a tree that is dying or dead. Bacteria, insects and fungus can enter these exposed areas weakening the tree until it falls down or cracks on it's own.