“How is the LogTag data stored and how can another person read this data when sent it?”

Downloaded data are stored in a LogTag Data file (*.ltd), which is a proprietary secure format that is tamper-proof. This is a requirement in many applications and standards (such as the FDA 21 CFR Part 11 in the US).
*.ltd files can only be accessed and viewed by LogTag Analyzer software, so if another person wishes to view the data on different computer then either they need to install LogTag Analyzer (which is free for download and use) or the data needs to be exported to another format.
LogTag Analyzer stores data in a folder which can be set in the Options, where you can also choose to automatically store data upon downloaded. LogTag Analyzer can export data either manually or automatically to formats capable of being imported by other applications such as MS Excel, however, data exported this way are no longer secure/tamper proof.