When we talk of the 'sanctity of life' we mean that life is not to be treated badly or discarded thoughtlessly. In terms of human life this often relates to our views on abortion, euthanasia and war etc.
Most religions believe humans are special.
Some religions, such as Judaism and Christianity, also teach that humans have been created in 'God's image'. It is also believed that humans have been given a responsibility to look after the world God created. You made him a little lower than the heavenly beings and crowned him with glory and honour. In other religions the sanctity of life is also taught. Thus all living things are to be respected.