What does output mean Will my bitcoin be there after syncronising  Am trying to sweep from my syncronising bitcoin core using my private key but its showing no output whats going on
An output is the spending part of a transaction, that establishes ownership of the funds. UTXO is an unspent transaction output. UTXO to your address are counted toward your balance. When you want to send Bitcoin, a UTXO is needed as an input to the transaction.

It is likely that if your node is syncing from scratch it doesnt know about the UTXO related to your address, yet. If it hasn't processed the block that contains the UTXO, it might not know about it, so it doesn't know you have a balance.  If you use the Bitcoin core wallet, there is a wallet database that stores that data.