Removal refers to removing old data, including the underlying data store.
Eviction is for removing from memory but maintaining the data on disk.
Removal is removing a node from the tree by the user on demand whereas eviction is automated remval of nodes based on the configured eviction policy. The eviction policy could be age based or time based. JBossCache has several eviction policy to choose from. Also, you can write your own custom eviction policy. Please see the documentation for more details. You can also register a cache listener to listen for changes on the tree and act on the emitted notification for a particular node.