Who is considered a third party

C. Securing means iwS
E. The form (in private law)
After discussing the guarantee, instruction, bill of exchange and check, guarantee contract and documentary credit, all of which are basically three-person obligations, the contracts in favor of and at the expense of third parties are to be briefly dealt with here, even if these do not have any direct reference to the security funds.
Usually, the legal consequences of a contract occur inter partes, i.e. between the parties involved in its conclusion. You are immediately entitled and obliged under the contract. - But it doesn't have to be that way. In the case of a contract in favor of third parties, it is agreed that the benefit promised in the contract (not only for the contracting parties, but) should be given to a third person (third party, beneficiary, beneficiary).
GlU 7355 (1879): The Promise recipient can demand fulfillment in favor of the (beneficiary) third party, ie sue them;
OGH 9/11/1974, 1 Ob 130/74 [Dittrich / Tades, MGA ABGB34, § 881 E 8]: For those shape of a contract in favor of third parties, the legal relationship existing between the contracting parties is decisive and not that with the third party. Therefore, in the above example (subscription), sales contract law rather than gift law applies.
SZ 29/53 (1956): The peasant handover agreement is a real contract in favor of third parties. As a lifelong treatise on assets, it represents an early succession - so-called successio antecipata - and contains numerous inheritance and family law components. It is a contract of its own, often a mixed contract, however, a uniform legal transaction that must not be broken down into its various components! - See the mention of the property transfer contract in Section 881 (3) ABGB.

Contract in favor of third parties
C as a third party, acquires his own right of claim against A if he does not reject the right arising for him from the agreement between B and A, ie accepts it; § 882 ABGB: The donation requires acceptance as a contract!
Differentiate the obligation of the debtor to perform - on the basis of the concluded basic transaction - and the right of the obligee to perform to the third party from his own right to claim the performance of the contract (against the promising party). - The contract between A and B is concluded on condition that C is accepted.
There is though Contracts in favor, no but at the expense of third parties. - § 880a ABGB only regulates the case that “someone promises another service from a third party” and adds that this is to be understood “as a promise of his use by the third party”; so-called Usage commitment: § 880a 1st half S ABGB. - If the person who promised “was responsible for the success [of the third party], he is liable for full satisfaction if the third party fails to perform”; § 880a 2nd half of the ABGB. Here lies a case of Guarantee in front. A Success promise makes the guarantor liable to pay compensation if the third party does not provide the service; NZ 1978, 158.
No contracts to the detriment of third parties
GlUNF 2512 (1903): The "Guarantee" of a mayor for the acquisition of a commercial license only means the use within his official powers within the meaning of § 880a 1st half of the Austrian Civil Code.
GlUNF 3281 = ZBl 1906/94: Als Success promise on the other hand, the seller's obligation to obtain a loan to the buyer to pay the purchase price applies. Third-party-financed installment purchase → CHAPTER 2: Third-party-financed installment purchase: §§ 18, 19, 22 KSchG.
As just noted, there are contracts in favor, but not at the expense of third parties. The latter contradict the essence of the Private autonomy and here especially the thought of Commitment and are therefore not permitted (without exception); see SZ 69/176 (1996): Sponsorship Agreement - Carreras, Domingo and Pavarotti in the Vienna Stadium.
C. Securing means iwSE. The form (in private law)