Alright kiddo, let me explain what trioecy means in really simple terms!
So imagine there are three kinds of plants, let's call them A, B, and C. Each of these plants has either male flowers, female flowers, or both male and female flowers. The plant with only male flowers is called a male plant, the one with only female flowers is called a female plant, and the one with both male and female flowers is called a hermaphrodite plant.
Now, trioecy is when there are all three types of plants in the same area, and they can reproduce with each other to create baby plants. This is different from dioecy, which is when there are only male and female plants and they can only reproduce with their opposite type.
So with trioecy, there can be some interesting things that happen! For example, the hermaphrodite plants can sometimes self-pollinate (that means they can pollinate themselves without needing help from the other types of plants), but they can also cross-pollinate (that means they can receive pollen from either the male or female plant and create a new baby plant).
Overall, trioecy just means that there are three different types of plants in an area that can reproduce with each other. Pretty cool, huh?