Just like Christians have Sundays & the Jews have Saturday. Muslims have Fridays.
Here's what many Muslims do on this day:
Everyone is told to shower/bathe, and encouraged to wear clean and good clothes.
The men are told to pray the afternoon prayer, known as Jumah (Friday) Prayer, at the mosque or public gathering. This congregational prayer replaces the regular midday prayer (Dhuhr).
They are encouraged to listen to the "khutbah", a sermon delivered by the imam (prayer leader). This sermon typically addresses moral, spiritual, and social issues relevant to the community.
The 2 MAJOR TAKEAWAY'S from this day: are that long before any culture even had the wildest hint of disease control and hygiene. Muslims we commanded to bathe once a week at least (bare minimum) & in an era before mass literacy and communication devices like books, tv's, radios, videos etc. Everyone was made to educate themselves via this weekly sermon.