A normal transaction will have previously unspent outputs listed as inputs, but a coinbase transaction is different. A coinbase transaction will always have a single input, called a coinbase, that follows a specific format. An overview of the transaction specification can be found here.

I've copied the example from that page below for convenience:

An itemized coinbase transaction:

01000000 .............................. Version

01 .................................... Number of inputs

| 00000000000000000000000000000000
| 00000000000000000000000000000000 ...  Previous outpoint TXID
| ffffffff ............................ Previous outpoint index
|
| 29 .................................. Bytes in coinbase
| |
| | 03 ................................ Bytes in height
| | | 4e0105 .......................... Height: 328014
| |
| | 062f503253482f0472d35454085fffed
| | f2400000f90f54696d65202620486561
| | 6c74682021 ........................ Arbitrary data
| 00000000 ............................ Sequence

01 .................................... Output count
| 2c37449500000000 .................... Satoshis (25.04275756 BTC)
| 1976a914a09be8040cbf399926aeb1f4
| 70c37d1341f3b46588ac ................ P2PKH script
| 00000000 ............................ Locktime