A copyright isn’t a single right; it is a combination of rights. Copyright owners can transfer some or all of the rights. A full transfer of rights is called a copyright assignment. It’s important for start-ups to get a full copyright assignments for their logo, website, software, etc that is created for the company by independent contractors or service providers.
If you have not received a full transfer of rights from the original copyright owner, the author of the work, you most likely do not own the copyright. Think of it like buying a CD. You own the CD, but the band or record label owns the copyright to the book and you are not able to copy and sell it.
If you do not own the copyright to your website or software for example, the developer of that material can resell it or use it as they please. It is critical that you receive a written copyright assignment from the owner of the copyright or its agent as you will need to present this when registering for your copyright.