Why Were Deepika, Sara Ali, Rakul Sent A Summon But Not A Warrant?

In drug case, NCB has sent summons to Deepika Padukone, Dia Mirza, Rakul Preet Singh, Shraddha Kapoor, Sara Ali Khan. After all, what is this summon, why does NCB send the summon, and who can send the summon and what is the provision of this in the law, watch this video to know.