What is low carbon energy?
Energy fuels and solutions that don't involve the burning and subsequent release of carbon into the atmosphere.
The world, more and more, consumes electricity; it's used to power out electronics, our household appliances, lighting, and so much more.
To generate that electricity, we need to generate it. As demand has been increasing for more and more electricity, we've been building more and more generating stations.
A common method of generating electricity is to burn things - the heat is used to make steam, which then turns giant turbines that spin rapidly and create electricity. Common fuels burned are coal and oil - both of which, when burned, release large amounts of smoke - carbon in an aerosol form that enters the atmosphere, interacts with it, and creates problems (for instance, an increase in carbon dioxide is directly responsible for climate change across the globe).
The push, then, is to find ways to generate electricity that does not involve the burning of carbon-based fuels, and preferably involves no burning at all - these solutions are what are called "low-carbon energy". Solar, hydroelectric, and geothermal solutions are all considered low-carbon energy.
Notice that we can also apply these labels to fuels we use to power vehicles. Currently, vehicles typically burn some form of oil-based fuel (such as gasoline) and this burning also causes carbon to be released into the atmosphere. This is way things such as electric vehicles are being researched and increasingly used.