Research is systematic inquiry: a question is asked carefully, evidence is gathered by a stated method, and conclusions are drawn that others can check. It differs from casual opinion because the method is explicit and the evidence is open to challenge.
Worked example: a teacher wonders whether group work improves test scores. An opinion would say "my classes seem better." Research states the question precisely, compares a group-work class with a comparable class taught the usual way, controls for starting ability, and reports both the result and the method, so another teacher can judge and repeat it.