What does the following apt-get response mean?

[Jim Byrnes]

Cybe R. Wizard wrote:
> On Thu, 2 Dec 2010 09:24:18 +0000
> Colin Law<clanlaw at googlemail.com>  wrote:
>
>> On 2 December 2010 00:03, Robert Holtzman<holtzm at cox.net>  wrote:
>>> On Wed, Dec 01, 2010 at 11:10:31AM +0200, Matthias Andersson wrote:
>>>
>>>               ..........snip...........
>>>
>>>>
>>>> In synaptic you need to check for that those packages aren't
>>>> locked to a specific version, you should see if this is the case
>>>> by pressing "status" in the lower left corner and then selecting
>>>> "pinned" in the left window.
>>>
>>> On my system (10.04.1) the status button does not show a pinned
>>> choice. Can this be because I don't have any pinned apps?
>>
>> You could try temporarily pinning one and see.
>>
>> Colin
>>
> Pinned apps never showed up in synaptic for me until I pinned one.  I'd
> guess that behavior to be standard.
>
> Cybe R. Wizard

In the context of this thread what does "pinned" mean?  I googled but 
never found an explanation.

thanks,  Jim