ている is a construction used in Japanese to convey that someone or something is existing in a constant state of ‘doing’ the verb that comes before て. In English, depending on the verb, this can be translated as ‘is (A)’, ‘am (A), or ‘are (A)~ing’. The expression is made by adding いる to the て form of either る-Verbs, or う-Verbs.

• シャンプーは何（なに）を使（つか）っているの？
  What shampoo are you using?
• 今（いま）ラーメンを食（た）べています。
  I am eating ramen now.

Due to いる being one of the verbs for ‘existing’ in Japanese, the ている form means something closer to ‘continuing to exist in a specific state’, rather than (A)~ing in English. This is why verbs like 死（し）ぬ, and 知（し）る, appear as the ている form in Japanese, when they would appear as the past form in English.

• お前（まえ）はもう死（し）んでいる。
  You are already dead.
• この人（ひと）誰（だれ）か知（し）っている？
  Do you know who this is?