Import <category> feeds field RSS

Hi! First of all I am newbie in Drupal.
I use Aggregator module to import rss feeds to my page. Everything works all right. The question is: can I use the field that comes in the rss xml? I need to categorize the feeds using that field and I don't know how to do it. Maybe I'm missing something in that module.. Probably using Feeds would be better.. but I've notice both are keeping other normal fields in database as tittle, description, url..
Please anyone could help me? have I got to develope a new module?
Cheers!