What is it?
Climate change is a natural process in which long-term global average temperatures raise (they can also lower) which, if it increases and accelerates can cause catastrophic consequences.
Causes
There is a process called "The Greenhouse Effect" this makes that certain gases that we can find in the atmosphere, keep heat and sunlight from escaping the Earth once they enter, that's why the long-term average temperature, or climate, keeps changing.
How are human activities related?
"The Greenhouse Effect" happens due to the gases released in the atmosphere, but which ones do we release?
The burning if fossil fuels, massive production of CO2, deforestation, and also the excesive pollution are accelerating that process causing the Earth's climate to basically go crazy.
Effects
Most of the effects of this situation are negative because of the quick increasing of temperatures, for example; the melting of glaciers, the destruction of many habitats, temperature rising abnormally in some places, droughts, coral bleaching, ocean acidification, changes in water and carbon cycles and sea level rising.