A full summary of Robert Frost's poem needs to, I believe, cover the content of all of the stanzas and refrain from making interpretive statements (as such statements fall under the topic of "theme" more than "summary"). To add to the first poster's summary in the first three sentences, then, I would add the following:
The first three stanzas make consistent use of the past tense. These stanzas are rich in imagery that present the two paths as different and yet the same. The fourth stanza contains a shift in time from the past to future. The speaker now reflects on how, some time in the future, he or she will look back and assign great significance ("all the difference") to the choice of one path over the other.
See the "meaning" section in the link below for another summary of the poem.