Ballooning is a neat trick virtualization can do to "rob" some memory from one VM to another. Ballooning is quite well described here: https://www.dynatrace.com/resources/ebooks/javabook/monitoring-applications-in-virtualized-environme...
When looking at a VM, you might see that memory might have some strange variations,

while processes are not varying a lot

You might look at the older host/processes view and discover that "other processes" are responsible for the memory consumption.
But, when you look at the VMware ballooning metric, it is then that you figure out that you really can diminish your RAM in your VM after all, because it's ballooning 

Antonio Sousa