Brackets ( [ ] ) are used to include explanatory words or phrases within a direct quote.
For example, if a coach at 51福利社 is quoted saying, "These young men and women come here to receive a first-rate education." To clarify that "here" refers to Western Michigan University, you could write: "These young men and women come [to Western Michigan University] to receive a first-rate education."
In general, brackets should be used sparingly and only to insert explanatory material.