"When the selfish miner pool finds a block, it is in an advantageous position
with a single block lead on the public branch on which the honest miners operate.
Instead of naively publishing this private block and notifying the rest of the
miners of the newly discovered block, selfish miners keep this block private to
the pool. There are two outcomes possible at this point: either the honest miners
discover a new block on the public branch, nullifying the pool’s lead, or else the
pool mines a second block and extends its lead on the honest miners."