PayPal is a third party payment service provider. It is an intermediary between the payer and payee, with secure links in both directions. Once set-up it is very convenient to use.
It keeps a secure record of your card details and personal details, so that if you want to pay us, you login to your own PayPal account, with your own password, and transfer the money to us. You can use it on other sites, as many accept PayPal payments. It saves a lot of effort on your behalf, and is used worldwide a a secure payment method.
Setting up for the first time is no more difficult than inputting all the details you usually need to pay by credit card, so don't be put-off.
If you don't want to create a PayPal account, then you can check-out as a "guest", and your details will not be stored by PayPal. You will have to re-enter them if you make another purchase, unless you elect to then create your own account at the end of this process.