The Holy Days are as follows:

Passover
Unleavened Bread
Feast of Weeks
Pentacost aka WhitSunday aka Shavout
Feast of Trumpets
Day of Atonement
Feast of Tabernacles

Likewise, there is also the the 7th year sabbath of the land and 50th year jubilee.

All of which are a shadow of things to come (Revelations).

No different than the name, most don't follow the Holy Days properly with arguments about how to observe the New Moon, and likewise the Holy Days.  It's through this that we can determine that the modern Jews don't follow the Torah and likewise the 10 commandments.  It's also likewise how various "churches" (like those spoken of in Revelations) fall short of obedience to YAHWEH and his commandments.  Modern Christians latch onto the fact that the "Jews" were bad, however they act no differently than the Jews of the time of YahShua and hence try to convert the "Jews" into their mainstream ideals of how Christianity should be, however they themselves are not Christians.  YahShua himself stated clearly "salvation is of the Jews"...with Romans 2 clarifying that a Jew isn't one by heredity, but by obedience to the Torah.  They may understand that there's merit to the 10 commandments, but they are likewise disobedient, and as such...they can't rebuke devils being devils themselves, and only cause people to hate YAHWEH with their pious behavior being hypocrites no different than the Jews of the time.