What does the parallax error take into account when measuring distance between two stars?

Related questions

• What is a parallax in regard to stars?
• What is stellar parallax?
• What does the term parallax mean?
• What is the parallax formula and how is it used to calculate the distance between two stars?
• What is the parallax angle?
• What is the description for the parallax technique for measuring the distance to the stars?
• Why can't astronomers use parallax to measure distances to other galaxies?
• What is the parallax formula for astronomy? What is the unit of measurement for the formula?
• What is the accuracy of the parallax method?
• What causes the angle of a parallax to increase?