In the simplest terms, energy efficiency means that you are using less energy to do the same task - for example, using a regular incandescent lightbulb requires more energy to generate the same amount of light than an LED lightbulb.
Not only does using energy-efficient technology cause less strain on the environment it also helps you save money by using less energy, without sacrificing quality or comfort.
Switching your outdated geyser for a solar geyser or exchanging your regular lightbulbs for LED's is an easy place to start. If possible, check the energy star ratings on newer appliances to see how energy efficient they are.
Regular home maintenance will also contribute to a more energy-efficient household. For example, a home that has proper insulation will require less heating during the winter months - which means lower energy consumption. Creating natural drafts throughout your home with open windows and doors at strategic points throughout the day will mean less aircon usage during the day.