Both chalazia and styes are eyelid bumps caused by blocked oil glands, but they have some key differences:

• Infection:
  A stye (hordeolum) is an infected oil gland, whereas a chalazion is a non-infected blockage. This is the main distinction.
• Pain:
  Styes are typically painful, while chalazia are usually painless or cause mild discomfort.
• Location:
  Styes tend to form on the edge of the eyelid, near the base of an eyelash. Chalazia develop deeper within the eyelid, further back from the edge.
• Onset and Duration:
  Styes appear suddenly and typically resolve within a week or two. Chalazia develop more slowly and can last for weeks or even months.