Efficient cause is the reason for something happening or being done in a certain way. It's like when you build a sandcastle at the beach - you're the efficient cause of the sandcastle because you're the one making it happen. Another example is when your mom cooks dinner - she's the efficient cause of the food being made because she's the one doing the cooking.
In other words, efficient cause is what makes things happen. It's the energy or force that gets things going. Just like how your body needs fuel to move, things need an efficient cause to happen.
Sometimes, the efficient cause can be something that is not always visible. For example, when a plant grows, the efficient cause is not only the water and sunlight that it receives, but also the genetic makeup of the plant itself.
Overall, think of the efficient cause as the spark that starts something. Without it, things wouldn't happen the way they do.