In mysql config use 'languages' to specify what languages your data will be available in. When an object is saved, CB checks for title_$lg fields and saves them in SOLR columns title_$lg_t. '_t' is used to specify a SOLR dynamic field. It doesn't matter if a content type has title_$lg fields, CB will always populate these SOLR columns, making sure each record has titles in all languages.
Each object has a SOLR 'name' field that is used if there is no 'title_$lg' field defined in content type. Example: filename of a file is used as 'name'.
When a record is displayed, CB will try to use SOLR title_$lg_t field. Same applies for object fields. Example: a product has 'color' field of type object. A thesauri content type is defined to have title_en, title_fr fields and used to create a few colors. The preview of the product will show language dependent color name.