O que significa then ?

See a translation

then is a very commonly used words and is a bit difficult to understand at first but once you become more comfortable with English will come naturally
Then usually refers to a specific point in the future or past but never the present after a certain amount of time
for example
Get me an apple
I will cook food
I will join these sentences using then
Get me an apple then I will cook
in this example then is still used to mark a specific point in the future but in context to the sentence marks a point after a certain action has been carried out this is another way then can be used
I will give you a few more sentence examples of then
then what?
this is a very common phrase and is a question asking that after this certain amount of time passes (the point in the future which then marks) what will happen

my explanation isn't very good I suggest you Google this for better explanations that will help you understand