Understand data sharing
By default, access rights to creator records is set to private so that the record owner and his/her manager can oversee the creator data. However, you can use Data Sharing to extend access rights to users belonging to other roles and groups. Once the data sharing rules are configured, users associated to other roles and groups can gain additional access to the records that belong to other users. The data sharing rule lets you configure the level of access for the records. The two types of access levels are Read only and Read/Write.