Afield is an adverb, and in modern English you almost always meet it with far or further in front. Far afield means a long way from home, or a long way from the place you started: we don’t often travel far afield means you mostly stay near home. Writers also stretch it. If a discussion goes far afield, it has wandered off the main question. You would not usually say afield by itself; it sounds unfinished, like a coat with one sleeve. Though actually, the oldest sense is quite literal. In Old English it was on felde, “in the field” — out of the house and onto the land. The “far from home” meaning grew from that picture of leaving the yard. It is a quiet, slightly bookish word. In speech people often just say far away or a long way off. It is not a farming word today, even though field is still sitting inside it.