Which among these categories of people are referred to as 'peers'?

The term "peers" has a very specific meaning in the UK political system, rooted in its history. It refers to members of the House of Lords. The House of Lords is the upper house of the UK Parliament and is distinct from the House of Commons, whose members are elected. Historically, the House of Lords was made up of hereditary peers – people who inherited their titles and right to sit in the House. Over time, the composition has changed, and now it includes life peers, who are appointed for their lifetime in recognition of their achievements. Bishops of the Church of England do sit in the House of Lords, but they are referred to as Lords Spiritual, not simply as "peers." Senior judges may also become life peers, but the term "peers" specifically and generally refers to the members of the House of Lords, reflecting their unique position within the parliamentary structure. So, while senior judges and bishops might be *in* the House of Lords, they aren't the category of people *referred to* as peers.