Hi iabc4,
Memory (RAM) and storage are not the same thing.
The solid state drive in your Mac serves as its storage. This is where macOS, along with all of your files, apps and settings, resides. Currently, Macs ship with a minimum of 256 GB for storage.
In contrast, memory (RAM) is where information is stored short term. Whenever you launch an app, its code (instructions) is put into RAM so that the processor or SoC can quickly access and execute it. When an app is running, it can also store certain data in RAM for quick access (for example, parts or all of a file that are being worked on). Currently, Macs ship with a minimum of 8 GB of memory (RAM).
If you get the message that you don't have enough memory, and you're prompted to force quit one or more apps, check which app is using the most memory (or isn't responding), and quit that app. The memory it was using will be given back to macOS, which can then allocate that memory to other apps as needed.
You're most likely running into this error message because one of your apps has a flaw in it, unintentionally created by the developer. This flaw is known as a memory leak, and it occurs when the app temporarily stores data in memory (RAM), but forgets to properly remove that data and give the used memory back to macOS. When this happens, the faulty app appears to just consume more and more memory, until macOS is forced to shut down the app and reclaim the memory it used.