Definition
A 3PL is an external warehouse partner that receives, stores, picks, packs and ships on your behalf. For replenishment, the 3PL is usually a warehouse stock source with its own receiving lead time and cut-offs.
Worked example
Supplier ships DAP to your 3PL. After ASN receipt and put-away, OmniRestock sees sellable stock; you then create FBA inbounds from that pool.
Why it matters for replenishment
3PL receiving days belong in lead time. Ignoring them makes order-by dates optimistic.
How OmniRestock uses this
OmniRestock connects Mintsoft, Linnworks and ShipBob (and CSV) so 3PL stock can sit in your warehouse model beside marketplace channels.