Terminal value is residual value which remains after exploiting all expected cash flow streams generated from asset or company as a whole. It can be related with liquidation value but it must not in any case.
It should be discounted to PV as each other cf streams.
For example, consider an asset (financial or what else) which supposed to bring you 10 K in first, 8K in second and 5 k in third year from now. After 3rd year from now, you have optinion to sell the asset for 1K which is its terminal value. Another approach does not consider a liquidation of asset than further constant term growth (after 3rd year in this example).