It is said that it is a temporary memory since the operating system of the device can erase it depending on the needs it has at all times, in this memory the data and instructions that the system needs to access are stored very quickly unlike the internal memory which is where they are permanently stored (until the system or the user decides to erase).
Therefore, the amount of RAM memory is a method to know how fast and fluid a mobile phone, tablet or smart watch can work, although it is not the only variable since it depends on the rest of the components.
Very few devices currently mount 12 GB of RAM as it is an excessively high amount for the normal needs of a mobile device. Only high-end or very exclusive devices currently incorporate this figure, although over time it will become popular as components become cheaper and mobile applications and video games require it.