Video Credit: The White House
The main target is Obama's Clean Power Plan, which would reduce the nation's dependence upon coal fired power plants even more than current economic conditions (cheap natural gas, increased usage of renewable energy sources, energy efficiency, etc.) are already doing.
Trump and his supporters claim the new executive order will result in more jobs for those in the energy industry, particularly coal miners. The latter group was represented by several miners at the signing who stood behind Trump as he signed the measure.
Additionally, the new order will open up federal lands to coal mining, eliminate requirements to reduce methane emissions from oil and gas production facilities, and reduce the importance of climate change impacts on permitting decisions.
The ball is now in the court of environmentalists, the alternative energy industry, and individual states who will be impacted by the potential increase in emissions and environmental degradation expected.