The purchase method and pooling-of-interests methods were used in the past for accounting for business combinations.
Pooling-of-interests use to take the book values of the combining companies, carry them forward to the combined company, and no revaluations to fair value were made. Nor were there write-ups or goodwill.
We feel, given that FASB eliminated the pooling-of-interests method and then issued ASC 805 to replace the purchase method, it is important to know that these methods existed. But not to go to much into detail.
The acquisition method is based on the fair value of the consideration for the combination (and plus any non-controlling interest not acquired). Goodwill does not need to be amortized. Therefore, with acquisition accounting, a base in the accounting occurs.