Three of the many features that are often present in Robert Frost's poems are a) a simple rhyme scheme, b) everyday language, c) multiple symbolic meanings.
For example, take the opening stanza from Frost's most famous poem "The Road Not Taken":
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;
The rhyme scheme in this stanza, which is repeated throughout the poem, is ABAAB. Simple.
In the 37 words that make up this stanza, not one can be considered challenging. Only "traveler" and "undergrowth" use more than two syllables.
However, this stanza, especially in conjunction with the rest of the poem, is full of different symbolic interpretations. First is the idea of a "yellow wood." Initially, this feels comforting. It brings to mind October and the changing of seasons. But this idea of change also brings about a sense of anxiety. Change is a scary thing.
Also, the idea of a diverging road is also a symbol that, for some, raises a certain level of anxiety. This image requires choice and when people make choices, it's very possible that they might make the wrong ones. This is possibly a reason why the "one traveler" was sorry he "could not travel both" and hesitated looking "as far as [he] could" to see where the road might lead.
While the above reading suggests struggle and anxiety, another reading of the same stanza could suggest possibility and empowerment.
The traveler has a choice in life, which is a good thing. How many people in the world are set on a path and required to follow that path to the end? The "yellow wood" could symbolize the fact that autumn, while it might lead to the quietness of winter, really just indicates the fact that one part of a human must die in order to give birth to another, perhaps stronger person.
These are just two examples of how something that seems so simple, is not. This is the beauty of Frost. He does not show off, nor does he attempt to be vague or ambiguous. He creates powerful images that allows the reader a myriad of ways of interpretation.