Properties are a set of key-value pairs associated with an entry.
There are two main applications for properties in Org-mode.
First, properties are like tags, but with a value. Second, you
can use properties to implement (very basic) database
capabilities in an Org buffer. For an example of the first
application, imagine maintaining a file where you document bugs
and plan releases for a piece of software. Instead of using tags
like :release_1:, :release_2:, one can
use a property, say :Release:, that in different
subtrees has different values, such as 1.0 or
2.0. For an example of the second application of
properties, imagine keeping track of your music CDs, where
properties could be things such as the album, artist, date of
release, number of tracks, and so on.
Properties can be conveniently edited and viewed in column view (see Column view).