Def Command

[Trinx]

I have a couple questions about the command "def". Once you define something, say "greeting", and you write your script in it:

def greeting():
name = input('What's your name?')
print('Hi,', name.title())
age = input('How old are you?')
if age > 18:
print('Nice.')

So you define greeting, but you want to continue that outside of the "def" command, like:

greeting()
else:
print('Oh')

Can I continue a "if then" statement outside of defining a variable? Also, I use "greeting somewhere, after python has run the script, will it continue down the script? Say I want to go to a specific spot of code depending on how the user input is answered, how would I do that? Thanks