Tertiary structure of a protein describes
The order of amino acids
Location of disulphide bonds
Loop regions of proteins
The ways of protein folding
Secondary structure denotes the configurational relationship between residues which are about 3–4 amino acids apart; or secondary level defines the organization at immediate vicinity of amino acids.
The tertiary structure denotes three dimensional structure of the whole protein.

Reference: Vasudevan 7th  ed, pg 38