From the website:

Geni is a tool for understanding and staying in touch with your family.
Geni lets you create a family tree through our fun simple interface. You can expand your tree by adding relatives' email addresses. They will be invited to join your tree and can add other relatives. Your tree will continue to grow as relatives invite other relatives.
Each family member has a profile which can be viewed by clicking their name in the tree. This helps family members learn more about each other and stay in touch. Family members can also share photos and work together to build profiles for common ancestors.
Geni is private. Only the people in your family tree can see your tree and your profile. Geni will not share your personal information with third parties. We will not sell your email address or spam you. Users control which communications they would like to receive from us.