IUI newbie , please help?

currently in my TWW , if i don't get a positive pregnancy test on 10/14 my husband and I will be moving on to our first IUI. 😳*unexplained infertility* 4yrs ttc

soo here's my questions i can use you ladies help, please answer what you can😊

-what are follicles , and why are the bigger the better?

-what is the trigger shot? how is it done?

-when is the best time in your cycle to start the meds/IUI process?

-how many appointments is it?

-did you get pregnant with your first IUI?

any other info would be helpful as well!! thanks so much!☺