What are manu, sku and cat in the qf parameter in SOLR?

Question

I was taking a look at the solrconfig.xml for the dismax parser and found a bunch of values such as sku, manu and cat. What are these?

 <requestHandler name="dismax" class="solr.SearchHandler" >
        <lst name="defaults">
         <str name="defType">dismax</str>
         <str name="echoParams">explicit</str>
         <float name="tie">0.01</float>
         <str name="qf">
            text^0.5 features^1.0 name^1.2 sku^1.5 id^10.0 manu^1.1 cat^1.4
         </str>
         <str name="pf">
            text^0.2 features^1.1 name^1.5 manu^1.4 manu_exact^1.9
         </str>
         <str name="bf">
            popularity^0.5 recip(price,1,1000,1000)^0.3
         </str>
         <str name="fl">
            id,name,price,score
         </str>
         <str name="mm">
            2&lt;-1 5&lt;-2 6&lt;90%
         </str>
         <int name="ps">100</int>
         <str name="q.alt">*:*</str>
         <!-- example highlighter config, enable per-query with hl=true -->
         <str name="hl.fl">text features name</str>
         <!-- for this field, we want no fragmenting, just highlighting -->
         <str name="f.name.hl.fragsize">0</str>
         <!-- instructs Solr to return the field itself if no query terms are
              found -->
         <str name="f.name.hl.alternateField">name</str>
         <str name="f.text.hl.fragmenter">regex</str> <!-- defined below -->
        </lst>
      </requestHandler>

Answer 1

Those are fields being searched for: SKU (stock keeping unit), manufacturer and categories.

Answer 2

you are probably looking at the solrconfig.xml that is provided as a SAMPLE, in order to be used with the docs to index at exampledocs/ directory.

These are the field names the sample docs (and schema) contain. It's just like a sample installation of solr.