Students are more excited to learn when they have a voice in what they learn and a choice in how they learn. Teachers have a role in providing learning scaffolding to ensure that lessons and projects are developmentally fitting and appropriate.
Students' voice and choice can contribute to a project at any point, from the "what?" of a project to the "how?" or even "why?" It can help differentiate projects for different learners in the room, and it can inspire engagement and ownership of the learning.
For more reading about voice and choice, check out the Edutopia blog.