What is the difference between free memory and available memory in the context of system resource usage?

Free memory is the amount of RAM that is not used by any program at the moment and is completely free for new tasks.

Available memory is the sum of free memory and memory that is occupied but can be quickly freed (for example, caches and buffers of the operating system). In other words, available memory is the actual amount of memory that the system can provide to an application without the need for unloading or swapping.

Example: if you have 8 GB of RAM, of which 2 GB are free, and 3 GB are occupied by cache that can be freed, then free memory is 2 GB, and available memory is 5 GB.

Therefore, to assess system resources, it is better to look at available memory rather than just free memory.