Snapshots, known as checkpoints in Hyper-V, come in handy when you retain to keep the last properly running state of a VM before deploying new software or installing an update. However, you have to be careful while deleting snapshots otherwise, you might lose important data. 

Read this post to learn how the Hyper-V checkpoints work and how to delete them using Hyper-V Manager or PowerShell without losing data.