Am new in this community,the rapid increase in technology and mathematics related to Bitcoin makes me confuse,am also concerned  about the safety of clients data since all transactions are done on a single public network.
 I brought up this topic because I want more explanation,if there is any development or means outside of the public Blockchain that also stores client data to ensure more privacy. I also learnt about lightweight wallet that connects to full node before any transaction,why is it so.....