This is the 9582nd most frequent Polish word.
wszyscy
"Everyone" or "all people."
In this sentence, 'wszyscy' is the subject and refers to 'everyone' who arrived on time.
Wszyscy przyszli na czas.
Everyone arrived on time.
Here, 'wszystkich' is in the accusative case as it is the direct object of the verb, referring to 'all my friends'.
Zaprosiłem wszystkich moich przyjaciół.
I invited all of my friends.
In this context, 'wszystkimi' is in the instrumental case following the preposition 'ze', meaning 'with everyone'.