Computer needs a lot of RAM?

Yes and this looks like this, my desktop has 16GB of RAM and needs 3GB throughout. My laptop same version of Windows 10 has 4GB of RAM but needs just under 1GB. What can this be?

To my knowledge, this is the memory management. The memory of a program, which has now been closed again, but still partially remains in RAM until the appropriate space is really needed. This has the advantage that the files are available faster. Disadvantages it has my knowledge - except for the psychological effect "I NEED MORE RAM! 111" none.

The laptop saves RAM at the expense of speed.

For most Windows systems perfectly normal! Most likely, there are already about 50 processes running idle at the beginning (possibly even more).

Startup and services open. Then disable everything unnecessary. Also the effects. If things go well, you will end up with about 25-30 processes. Windows uses analogously to the increasing RAM and always!