Family sharing
What can they see from my phone, like can they see my photos, app, music, notes?
Files such as photos and notes aren't shared automatically. There is a Family Photo Album that is shared between family members, but you must add photos to that album in order for them to be shared between family members.
Your purchases such as music and apps can be shared between family members, but every family member has the ability to enable or disable this feature.
For more complete information, here's an article on the subject: What is Family Sharing? - Apple Support