Green house gases r those which increase heating up of the earth. they increase the rate of global warming. increasing rate of green house gases is the present debate at the national  level  meet of various country leaders. the problems faced by it have enormous effect on lifestyles of people. they cause skin rashes, skin cancer, change in climate pattern, rising temperature, increasing sea or water level, extension of many aquatic animals, displacement of various people of coastal areas. 
Greenhouse gases are very harmful to the human environment. But these are helpful in growing plants. As carbon dioxide is a greenhouse gas but it is harmful to human beings. it causes many harmful diseases, infections, rashes etc.examples of green house gases are methane gas and carbon dioxide Etc.I hope this answer helped you.