Atomic multipath payments
Atomic Multipath Payments (AMP) are payments that use multiple paths to complete a transaction that either all complete successfully or none complete successfully.
One of the problems the lightning network has had is limited ability to send higher-value payments, because of limitations in channel capacity along possible routes to the payee. Using AMP, a payer can send a payment using many paths, which can make larger payments far more reliable.
AMP is not yet available yet on any lightning implementation, but non-atomic multipath payments (MPP) were recently implemented by LND in v0.10.0. MPP is the first stage in a three-stage process for AMP. The second stage is hash-based AMP, and the third step is a better form of AMP that uses points and scalars instead of hashes. The third stage requires Eltoo and Schnorr.