CSLI, or cell-site location information, is the data held by third parties (typically cellular companies like AT&T or Verizon) for business purposes in order to provide better service to their customers. When a person uses their cell phone to make a call, send a text, or access an application that requires the use of data, the phone connects with the cell tower, and the activity is stored. The data is retrieved and stored in cell towers. This data has the ability to provide time-stamped locations of the phone.