Hey @hunght, Welcome to the Dgraph Community!
Badger is an embeddable key-value store. It’s CLI tool is not meant for DB operations like inserting an entry or getting a value. It is for more general purposes like creating a backup of whole DB, restoring it, testing(benchmarking) badger etc. For details on how to use Badger, you can refer to its README.
Feel free to ask more questions.