Colocation refers to the placement of your physical server in a data center rack. You can either share a rack or rent the entire rack. After that, the colocation partner takes care of internet access, network infrastructure, and power backups.
Dedicated hosting solutions imply that you purchase or lease physical servers that will be used for your specific needs.
Co-location is similar to dedicated hosting, but it refers to your hardware. Dedicated hosting typically refers to leased servers that a provider sets up in their datacenter and grants you access to.
