Whats the main idea to this poem?

the road not taken
by robert frost

two roads diverged in a yellow wood,
and sorry i could not travel both
and be one traveler, long i stood
and looked down one as far as i could
to where it bent in the undergrowth;
then took the other, as just as fair,
and having perhaps the better claim,
because it was grassy and wanted wear;
though as for that the passing there
had worn them really about the same,
and both that morning equally lay
in leaves no step had trodden black.
oh, i kept the first for another day!
yet knowing how way leads on to way,
i doubted if i should ever come back.
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.