Yes, you own the website and you can make changes at any time if you wish. You need to have a licensed copy of a Web design software and know how to transfer files to and from your live website (which are included in our website hosting setup documentation that is sent to you at the time of hosting).
As we designed you website, it would be easy for us to do changes and you may want to sign-up for one of the website maintenance contracts as appropriate to you. Maintenance contract is a separate service and is NOT required to get web design service from us.
We also offer some good online tools (add ons) to help you with content and picture changes on your website. You might ask for more details if you're planning to update your website yourself. If you're getting a eCommerce or database solution from us, those tools give you a back-end where you can define and update content on your website fairly easy.