There are four major rendering kernels in OctaneRender™ : Direct Lighting, Path Tracing and PMC and Deep Channel.
They are switchable by changing the type in the Node Type combo box.
In general, “directlighting” is used for drafts (although can be used for final copy), “pathtracing” and “pmc” are used for high quality rendering, and “deep_channel_kernel” is used for analytical output.