When computer code encounters the word “if,” what does it do?

I'm taking a class on how to make a movie, and it offers some apps that would be in the process. the thing is, i don't have any of those ha. if you have any tips on some apps i could use, that would be awesome. i don't have an iphone, so don't suggest any apps like imovie. i know that this is a weird question, but it would be super for me. : )

How might the success of your campaign be affected if you haven’t carefully completed all field data or if you accidentally insert the wrong merge field in the document?

Alcohol’s affects on the cornea and lens of the eye make it more difficult