Connotation:
The non-literal, associative meaning of a word; the implied, suggested meaning.



Example:
And on a day we meet to walk the line
And set the wall between us once again.
We keep the wall between us as we go.
To each the boulders that have fallen to each.
-Mending Wall


Explanation:
The word "wall" acts as both a boundary (an actual wall) and also an emotional barrier that prevents interaction between  the narrator, and his neighbor. The connotation of the word wall, makes the poem much more interesting. This connotation could also be said to be a metaphor. The purpose of the this connation is that the readers can relate to it, and it also adds a special effect to the poem. It makes it unique, and not boring by just out right discussing the barrier between him and his neighbor.