What is the difference between discretionary and non-discretionary portfolio management services?

There are two types of PMS offered by companies, one is Discretionary PMS and Nondiscretionary PMS.

• Discretionary PMS: The buy and sell of securities decisions are made at the portfolio manager's discretion.
• Non-discretionary PMS:- In this the buy and sell of securities are made as per the directions of investors. But the portfolio manager suggests the ideas.