Direct Memory Access or DMA is a simple concept to grasp. As the name implies something is accessing host memory directly—presumably bypassing something else. In the case of an ANIC adapter, it is the one directly accessing host memory and bypassing the host CPU in the process. In other words, with DMA the host CPU is not burdened with having to deal with copying data from the ANIC adapter into host memory for consumption by the host application.
Since the CPU is not burdened with this processor intensive task, it is free to perform higher value functions which is ultimately the purpose of using an ANIC adapter in the first place. So simply put, after all packet processing concludes, an ANIC adapter efficiently transfers all relevant packets and associated packet descriptors (metadata) across the PCIe bus directly in to host memory for consumption by the host application.
For a complete review of all ANIC adapter features please see below.