Windows 7 - Diff.between "available" and "free" physical memory?

When I look into the "Performance" tab of my TaskManager then there are the following values:

Total: 4014
Cached: 1299
Available: 2697
Free: 1532

Hmm, What is the difference between available and free space?
Shouldn't this be the same?

What means cache?

From my point of view there should be a value "occupied by running prgms" and "free".

Peter

Available is the only one that matters. Available shows what is capable of being used by Programs. Without paging other lower priority processes out of memory. It is a combination of both Cache and Free.

Plus the current memory handling architecture for Win 7 is that it tries to front load possibly needed libraries into memory to help speed up things. The free part is basically the memory that doesn't have any front loaded material at all. For the most part, as Logicearth pointed out, Available is the one that you should trust more, as the frontloaded libraries are easily forgotten in favor of making room for needed memory.

As others have said, Windows 7 will preload things into RAM when your computer isn't busy...this way when you do need or want them, they launch much faster.

In your chart above, the free (totally unused) + cache (that which has been preallocated) should just about equal the available amount. The available is going to show just a bit less than these two summed together.

In any instance that you need more RAM than what is Free...Windows 7 will just use the cached memory and dump what is there.

If you have the memory, might as well use it. It does no good if it sits there totally unused all day long.

This is a good article.

Measuring memory usage in Windows 7 | BrandonLive

Unfortunately there is a bug in Windows 7 related to NUMA (non-uniform memory architecture) that will cause issues on certain platforms when the amount of Free memory goes down. For instance, on my Thinkpad T410 with 8GB of RAM the Free memory will approach zero when I load a large VM. When I stop the VM and exit VMWare, the Free memory does not recover - the memory remains allocated by the cache.
The problem with NUMA is that it prefers to allocate memory from banks that are attached to a CPU core (hence non-uniform, i.e. not all memory is considered equal). Unfortunately, the Windows 7 NUMA bug prevents memory from being allocated that is in the Available pool in this scenario. Since I have no Free memory, the machine begins to swap madly when I restart the VM (the same or another one does not matter) and freezes up for minutes - even though there are over 4GB "Available".
So, despite of what the others have said, the amount of "Free" memory is more important than what's in the "Available" pool.

There is a hotfix for this issue:
Poor performance occurs on a computer that has NUMA-based processors and that is running Windows Server 2008 R2 or Windows 7 if a thread requests lots of memory that is within the first 4 GB of memory

Look into Resource Monitor > Memory tab. That gives you a better picture. The nums in Task Manager can be confusing. Everything you see in blue, is up for grabs by more programs/processes/data. The orange is temporary and still needs to be written back to disk, the green are your running process/data and the grey is hardware reserved (e.g. for graphics).