Understanding Notifications

having trouble using and understanding the messages that Reminders and Calendar give on my IOS and MBP. I dont kniow the correct terminology for them but i would call them reminders, or notifications... the message that pops up on the iphone to say 'meeting in 1 minute' or whatever you want reminding. I dont understand how to use them as i seem to gwet bogged down in multi multi reminders fro the same thing, i get rid of a reminder and i dont know if i have got rid of it for good or not, have a cancelled it, can i put the reminder off at all... but i see mt oend up with them all coming back at once and i have to click through them all, where there are several duplicates in there, to be able to do anything on my IOS device...

in short i really need a guide to how to use them. Is there one? Maybe i can then tailor my use to who they are meant to be used...