<em>Ein </em>=> is for <em>nominativ</em>, <em>der, das</em> or <em>akkusativ</em>
<em>Eine</em><em> => is </em>for <em>nominativ,</em> akkusativ, singular or Plural die .
for example,
das Auto => ein Auto
die Tasche => eine Tasche
der Bleistift => ein Bleistift
This is hard to translate into English because in English there is no change between masculine and feminine for the articles.
Hope this helps ^-^