What are the connotative meaning of plots in the poem "The Road Not Taken" by Robert Frost?

A connotative meaning is an applied or secondary meaning.  A denotative meaning is the literal or surface meaning.

In this poem, the denotative "plot" is that there was a yellow wood (an autumn wood) in which two roads went in different directions.  The speaker is standing at the point where they diverge and trying to decide which one to take.

If we look beyond the literal, then the autumn wood can represent the autumn of life.  The road represents too separate paths in the speaker's life.  The speaker is trying to decide which path to take.  One path seems "less-traveled" than the other, although the speaker admits he can see little difference.  However, he implies that his "less-traveled" path is not the one usually taken by adults.  It seems mysterious and exciting.  The speaker is trying to decide - do I follow what everyone else has been doing, or do I try something different?  The speaker decides to try something different; he "took the road less traveled."  He says with a sigh that this "has made all the difference."  We are left to feel that this decision was a wrong one.  The speaker makes sure we understand that he can't go back and change the path he chose, and the solemn nature of the poem suggests that the path was a poor choice:

I shall be telling this with a sigh

Somewhere ages and ages hence:

Two roads diverged in a wood, and I—

I took the one less traveled by,

And that has made all the difference

We are finally left with the sense that life is full of decisions which must be made, and that "somewhere ages and ages" in the future, we may look back and regret or blame our choices.