This shows that I don't have Apache installed. If I did, then the version installed would show after "Installed:" - instead of "(none)". If I was going to I would get 2.2.22-13+deb7u5 (i.e. the "Candidate:"). Then it shows all the latest versions available and from which repo. So 2.2.22-13+deb7u5 comes from from the Debian security repo.
Also keep in mind that this info relies on the local package database so it's good practice to update that too. So unless you've run apt-get update lately this is probably the way to go:
I recommend 'apt-cache policy'
So on my Wheezy desktop system this is what I get:
This shows that I don't have Apache installed. If I did, then the version installed would show after "Installed:" - instead of "(none)". If I was going to I would get 2.2.22-13+deb7u5 (i.e. the "Candidate:"). Then it shows all the latest versions available and from which repo. So 2.2.22-13+deb7u5 comes from from the Debian security repo.Also keep in mind that this info relies on the local package database so it's good practice to update that too. So unless you've run apt-get update lately this is probably the way to go: