For Zcash and Zcash-forked coins (like ZelCash), freshly minted (coinbase) coins must be shielded to make them spendable. Your ZelNode rewards are received by you as coinbase coin, as they are sent to you directly from each block find. The shielding action will send your coinbase coin to a private address (Z-address) of your choosing, which will shield them. From the Z-address, you can send the shielded coins back to a transparent address (T-address) of your choosing, like your light ZelCash address in ZelCore, and your rewards are now spendable and can Tx anywhere.