APA means Asset Purchase Agreement and is an agreement by which a business purchaser agrees to purchase the assets of a business (but not the business entity itself and not the business debts).
APAs are the most frequent type of business purchase in the Main Street tier of business purchases and sales and are much less complicated than the sale of a business itself (i.e. through a sale of the stock of the business if it is a corporation, or membership interest if it is an LLC).