The earths climate has remained relatively stable for most of human history. This is evident from temperature records some of which date back to the mid-1800s and before this based on reconstruction from other records and measurements e.g. tree rings. Since about the middle of the 20th Century an increasing trend is evident in the global temperature record. This is frequently referred to as global warming, but the term can include other changes such as melting of ice and thermal expansion of the oceans which is a major contributor to sea-level rise.

Broadly speaking, we need to focus on two things to address climate change: mitigation and adaptation.
To mitigate climate change, or avoid the worst consequences of a warming world, we must reduce the concentration of greenhouse gases in the atmosphere. That means reducing emissions. If we want to limit warming to 1.5 C, we must cut global emissions by half by 2030 and reach net-zero (when there’s a balance between emissions produced and emissions removed from the atmosphere) by 2050.
Burning fossil fuels like coal, oil and natural gas is the largest source of emissions, so we need to stop extracting and burning these resources. We can do this by conserving energy and by choosing clean electricity over fossil fuels. We can also reduce emissions in the atmosphere through nature-based climate solutions like planting trees and restoring wetlands and forest ecosystems.