Plugin development

Hello all,

I want to know how to make a plugin in which
1) a user can see a product on one page with buy button
2) on the order page where he could fill all the details about himself 3) and then he will be redirected to paypal for payment

Please let me know how to make i don’t want to know about plugins i just want to know how to do it by myself for study purposes.

Thank you
Arsalan khan