Robust things, like robust plants or animals, are strong, sturdy, and healthy. They seem to have lots of power and energy, and they won't break easily. And robust foods and drinks have a strong flavor.
Look how robust this flower is! Its leaves are thick and strong. It's wide and beautiful, growing amid the harsh rocks, ready to withstand challenges like low sunlight and little rain. It's a survivor. It's robust.
Pick the word "robust" to describe something that surprises you with its strength and power. Normally we think of flowers as delicate and breakable, but if you find a strong flower, call it robust. Normally we think of ants as tiny and easily squished, but if you see some ants carrying away an entire sandwich, call them robust. And normally we worry that very old people will fall and hurt themselves, but if you meet some strong, muscular, energetic 90-year-olds, call them robust!
Finally, let's get abstract! If you have excellent math skills, and if you're ready for a math challenge, ready to power your way through the hardest problems, then your math skills are robust. If you have an excellent vocabulary, and if you're ready to pick precise words to express all your ideas, then your vocabulary is robust. And if your community is strong, filled with people who know each other well and take good care of each other, and if your community overcomes terrible struggles, then your community is robust.