The ISP provider gives you access to some space on his server. You need to setup a database on this server. Once you setup a database, you need to add tables to your database. The tables contains the data you want to pull out. For example, the table cotains your product information, customer information, etc. This is one side of the story.
You want your clients(who sits infront of their browser) to see what products you have. But you will not let the client to go to the database server (also this is not a good practice). So you will allow him to send a request to the web server. The web server in turn send this to the SQL server. The SQL server processes this information and sends a result to the web server which will package this into an HTML page for you to see. This is what generally happenning.
HTH