This is PrestShop module that allows to log in with paypal to your online store. Addon also creates an account in shop (register customer). Module adds button to most important places in shop (from order process and customer register process point of view)
more informations about this module you can find here:
log in with paypal to your online store
You can find there only valuable solutions for your e-commerce shop based on PrestaShop engine. Search the best plugin for your store that will meet your requirements and just use it.