How is eggs made of oviporus animals? I know it's externally fertilized but how automatically and eventually???

Dear student,
Please find below the answer:

Oviparous animals lay eggs and these are fertilised externally. This can be understood with the following example: A hen lays around 5-6 eggs in a day. All the eggs laid by the Hen in a day might not be fertilized. This is because the eggs will be fertilized if a Rooster is involved or Mate with Hen. Hen does not need a Rooster to lay an egg but to get her egg fertilized it requires a Rooster.

So, fertilisation of an egg by a roster, in this case, is a chance event.

Hope this clears your doubt.
Regards.