Fixed star
A fixed star is one of the stars proper, called fixed because it holds its place in the constellations while the planets wander among them.
They are not fixed at all: precession carries them forward through the tropical zodiac at about one degree every seventy-two years, which is why a star's position has to be given for a date. Aldebaran and Antares sit near the start of Gemini and Sagittarius today, and did not a thousand years ago.
Classical practice reads a star only when a planet or an angle is within about a degree of it, and the tradition is emphatic that a conjunction to a bright star is loud rather than automatically fortunate. Regulus, Algol and Spica carry the strongest reputations, in both directions.
Frequently asked
How close does a star conjunction have to be?
About one degree, and many authors tighten that further. A star is a point, not a body with an orb of its own.
Why do star positions change?
Precession moves the tropical zodiac against the stars by roughly one degree every seventy-two years, so a position is only valid for a stated date.