Parallelism is a rhetorical device where parts of a sentence or a series of sentences are constructed similarly to convey equal importance. This structural arrangement ensures balance and symmetry in the expression of ideas. The elements that are parallel often have a similar grammatical structure, making the writing more clear, effective, and aesthetically pleasing.

For example:
- Not Parallel: He came, saw and conquered.
- Parallel: I came, I saw, I conquered.

In the context of the question, the structural arrangement described is characterized by placing elements of equal importance similarly.