This is the 409th most frequent Czech word.
všichni
"Všichni" means "everyone" or "all" in English.
Here, 'všichni' is used as a pronoun subject, meaning 'everyone', referring to all individuals in a group.
Všichni byli nadšení z nového filmu.
Everyone was excited about the new movie.
Here, 'všichni' changes to 'všem', the dative plural form, as it represents the indirect object 'to everyone'.
Všem se to líbilo.
Everyone liked it.
In this case, 'všichni' changes to 'všechny' in accusative plural form, as it is the object of the verb 'invited'.