You group data to be replicated in an object called a publication.
A publication is made up of one or more articles.
* Articles
An article is an individual set of data that is to be replicated.
An article can be an entire table, a subset of a table consisting of certain columns or rows, or a stored procedure.
You create subsets by using filters.
A filter that is used to create a subset consisting of rows is called a horizontal filter.
A filter that is used to create a subset consisting of columns is known as a vertical filter.
* Publications
A publication is a set of articles grouped together as a unit.
Publications provide the means to replicate a logical grouping of articles as one replication object.
For example,
you can create a publication to be used to replicate a database consisting of multiple tables,
each of which is defined as an article.
It is more efficient to replicate a database by replicating the entire database in one publication
than by replicating tables individually.
A publication can consist of a single article, but it almost always contains more than one article.
However, a subscriber can subscribe only to publications, not to articles.
Therefore, if you want to subscribe to a single article,
you must configure a publication that contains only that article and then subscribe to that publication.
Source: Microsoft SQL Server 2000 Administrator's Companion Book