Yes, other devices such as tablets can also be locked by the carriers you purchase them through.
Carriers lock their devices until you have either paid them off or purchased them outright. Having a device locked is a carrier's security tactic with their devices.
If a device is locked you can't switch carriers. However, once it is unlocked you can take it to any compatible carrier.
Click below to see some WhistleOut Guides on Unlocking Devices