So you've installed Solr 1.4 and you've managed to get some data indexed. Now you're ready to have some fun with faceting. Faceting is basically just filtering the results of a search without effecting the relevance score. Sites such as ebay use faceting to help narrow down the results of a generic search like TV, to give you options such as 32" wide-screen LCD etc.
It makes for a very pleasant user experience. It's one of the main reasons to use Solr and Solr makes this process very easy. There are actually 3 types of faceting. In this post I'm only going to talk about "field faceting". Once you've mastered "field faceting", the other 2 types ("query faceting" and "date faceting") are very easy and the basic Solr Wiki will be enough for you to get going.
Now when you're indexing data in Solr, it's best to use the "text" field type, as this applies lots of filters which will help sort out plurals, remove white space etc. However when it comes to faceting, the values returned will be the values after the filters have been applied. Therefore it's best to create new versions of any fields you wish to facet.