That's an 'eclipsing binary'.
"Occulting binary". The word "occult" means hidden or in shadows; if a binary star's orbital plane happens to be exactly through the Earth's path, we might see two stars when they're separate and then see one of the stars disappear behind (or in front of) the other.
Algol
Precisely by the eclipse - that's what an "eclipsing binary system" is all about. The idea is that one of the stars partially (or completely, in some cases) covers the other star; with the result that the combined brightness (as seen from Earth) gets less for some time.
That happens in an "eclipsing binary".
Each of those is an eclipsing binary.
The dimmer, secondary star passes in front of the brigher primary star, dimming it.
Generally the main star as this will have the most mass. However, temperature is not necessarily based on mass, so a secondary unit, could well be hotter but less massive.
Because in eclipsing binaries, the two stars orbit each other regularly passing in front of the other, blocking out some or all of light of the hidden star.
The Algol star system is known as an eclipsing binary pair, As such, one star moves in front of the other, blocking it's light. Because the pair are in line with the Earth, it has the effect that one stars seems to disappear. See related link for an animation of the effect.
Star system with 2 star called? binary star system
eclipsing