What are jumbo reverse mortgages and how do they work?

My mother lives in our family home in the San Francisco. In the current market it's probably worth around $800K although it has been worth more in the recent past. My mother is on a fixed income and one of her friends who lives outside the city took out a reverse mortgage on her smaller and less expensive home awhile back. This friend of my moms now has a little more money and my mom seems to think that she should do the same. When this first came up I talked with a financial planner and we all agreed that a reverse mortgage was a bad idea, but now she's been telling me about jumbo reverse mortgages and I'm wondering how do jumbo reverse mortgage work and what makes them different? Is it really something different and should I talk to the financial planner again?