Long set of figures & numbers (not an email address and password)

I guess deppends on what you are buying for example steam it can be a 4x5 or 7x5 number+letters combo like aaaa1-bbbb2-etc.
If you buy an acount and dosent matter from where yeah you should get email+pw.

Figures and numbers which can be copied and pasted, a straight key on their website which can be accessed whenever needed

The key is collected from the website after payment and comprises blocks of random letters and numbers which need to be entered when installing or opening the product.

It will usually be a long set of alphanumeric characters, or whatever the target system uses. Then just copy and paste into your target system or application.

They have a section of the site called Autokey. This is where your keys are created and used.