The ne character 呢 (ne) is a special character that can be used in two ways, to ask a reciprocal question, or to add mood to a question or statement.
Using 呢 to ask a reciprocal question
呢 (ne) can be added to the end of questions to add a perplexed, puzzled or questioning tone to the question making it a reciprocal question. Here are some examples:
Where did he go?
他去哪儿？ (tā qù nǎr?)
Where could he have gone?
他去哪儿呢？ (tā qù nǎr ne?)
Why are you cooking?
你为什么做饭？ (nǐ wèishénme zuòfàn?)
What are you cooking for?
你为什么做饭呢？ (nǐ wèishénme zuòfàn ne?)
What about you?
你呢？ (nǐ ne?)
Using 呢 as a modal particle in a statement
呢 (ne) can be added to the end of a statement or sentence to add a convincing tone or mood. When used in this way 呢 is referred to as a modal particle, that is they essentially communicate the mood of what the speaker thinks about the sentence.