DRAM also has to be refreshed. The data is stored as a charge on a capacitor - and a rather leaky capacitor at that. So, you can think of data on a DRAM like being a drawing on an etch-a-sketch that is strapped to a paint shaker.
So, for DRAM, you have to , every so often, read back every memory cell and re-write the data to make it stronger. The data is organized in a row/column format. Every so often a row will be refreshed. After a little while, the next row if refreshed. Later still, the next row is refreshed. You get the idea. This way, all of the data stays fresh.