In the sailing community this is also known as single-handed sailing. It entails sailing alone without any other person present on the vessel. Wikipedia describe it as single-handed sailing as with only one crew member or one person on the vessel.
Single-handed sailing is more suitable for short distances or protected waters with comparatively low or less difficulty. The vessels used are mostly smaller class boats.
There are single-handed sailing that goes around the world. Under these circumstances there could be others on deck attending to more specific functions.
Sailing along or single-handed sailing does not mean that it is a non-stop sailing. It is different from single-handed racing that could be Transatlantic or other longer competitive distance races.
When someone is sailing alone, the person should be fully aware of the hazards. Falling overboard is one of the most common hazards. In this situation one can float away from the vessel while the vessel is on auto pilot and sailing away from the person. The widely accepted navigation rules of sailing require one to be acquainted with the environment and to be fully alert. The other hazard could be collision at sea. This could happen while sleeping or resting.