On a superficial level, the speaker needs to decide which path to follow through the woods. Both paths appear to be untraveled as the speaker studies the undisturbed leaves on the surface that morning. Neither seems to be particularly preferable because it would be easier or more scenic. The only apparent difference seems to be that one path appears to be less used than the other; the speaker decides to follow that path.
On a deeper level, the speaker may be faced with a decision point at a late point in life; in the autumn season, s/he needs to determine a direction for the remainder of his/her life. Either of the two choices would be acceptable, and the speaker is regretful that it will not be possible to follow both options. However, the decision is made to follow the road "less traveled by" - to follow the less common option or life choice. The poem ends with the speaker recognizing that this is a life-determining decision "that has made all the difference."