A monocarpic plant is a type of plant that only flowers and produces seeds once in its lifetime. It's like a caterpillar turning into a butterfly, but instead of changing forms, the plant grows to its fullest potential and then dies after it has produced seeds.
Imagine planting a seed and watching it grow into a plant. This plant will go through different stages of growth and eventually it will produce flowers. Once the flowers have bloomed, they will produce seeds. And once the plant has produced seeds, it will wilt and die.
Some examples of monocarpic plants include agave, bamboo and some species of palm trees.
So basically, a monocarpic plant is like a one-time deal, once it has produced its offspring, it's done for good.