What is a website owner?
Usually the person or company who purchased the domain name that is used to access the website. Without a domain name a website is not accessible from the internet. You can also specify who the owner is when purchasing the domain name.
When a website is 'under construction,' it means that the owner or developers of the website are coding the website to make sure that it has all the functionality the owner wants it to have. A website is like a building, it must have foundations, and decorations, and that is why the term 'under construction' was coined.