Hadoop supports shell-like commands script for interaction to HDFS directly and other file systems that Hadoop supports. You can use the following command to know the list of shell commands supported by Hadoop.
bin/hdfs dfs -help
Use the following command to see the more detailed help for a command.
bin/hdfs dfs -help command-name
These shell commands are used for operations like copying files, changing file permissions, changing replication of files, etc.
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I recommend watching this video on how HDFS works for a better understanding: