title: Time series: What is a "non-zero mean"?
body: <p>I am looking through a few related posts on the topic and often landed in medias res. Therefore, please allow me to ask three directly related questions on time series:</p>
  
  <ol>
  <li>What is a time series with a "non-zero mean"? </li>
  <li>Does it mean that it has an "intercept", or also named "constant"?</li>
  <li>When a time series has a "trend", does it just mean that it trends
  up or downwards?</li>
  </ol>
  
  <p>I considered <a href="https://stats.stackexchange.com/questions/44647/which-dickey-fuller-test-for-a-time-series-modelled-with-an-intercept-drift-and">this post here</a> but couldn't fully answer my questions from the example.</p>
  
  <p>Thank you!</p>