A. These two terms are very important for investors.
Investment fiduciaries are legally bound to act in your best interest, even at the cost of their own, when giving advice or recommendations. Registered Investment Advisers (RIAs) are held to a fiduciary standard.
Security brokers adhere to a less-stringent suitability rule - the investments they recommend to you must be suitable for you, given your goals, age, risk tolerance, etc. However, such investments might not be, say, the lowest cost alternative you can choose.
When do the differences matter the most?
It typically happens when you leave your current employer. 401(k) plans always have a fiduciary (usually your employer). If you leave your employer and meet with a broker to discuss your options of dealing with your 401(k) assets, you might frequently be pushed to rollover your 401(k) accounts into IRAs, this might or might not be a good move for you, but one thing is certain - the brokers will reap higher fees.