If you use a shielded Zcash address to send and receive ZEC, your transaction history and wallet balance are not traceable. It’s like spending cash at a grocery store: There’s no publicly viewable record of where that money came from or who spent it. If you use a transparent Zcash address, then your holdings and financial history are publicly available (like Bitcoin). Some Zcash wallets now autoshield funds they receive from transparent addresses.