Actual change of possession

What does Actual change of possession mean in American Law?

The definition of Actual change of possession in the law of the United States, as defined by the lexicographer Arthur Leff in his legal dictionary is:

Under most pre-U.C.C. versions of the statute of frauds, one of the happenings that would render an otherwise unenforceable unwritten contract for sale of goods enforceable was actual receipt by the buyer of some of the goods. Partly because of the usual wording of the statutes, and partly for reasons of policy, it was generally held that the receipt had to be actual and physical rather than symbolic, e.g., still in the seller’s warehouse but with a sign attached indicating the buyer’s ownership.

Under the U.C.C. version of the Statute of Frauds (§ 2-201), otherwise unenforceable contracts are enforceable with respect to goods which have been “received and accepted,” with the meaning of the latter phrase the subject of § 2-606.