Smaller parts of a bigger project.
Subprojects are like pieces of a puzzle that make up the whole picture.
Examples:
We have several subprojects to complete before we finish the main project.
Each person is responsible for a different subproject.
The subprojects are like small jobs that together make a big job.
The subprojects are like the ingredients for a cake - you need them all to make it.
There are many subprojects, but they all help to make the big project better.
The subprojects are like the different colors in a painting - they all come together to make something beautiful.