A 'Channel Selector' in Apache Flume is responsible for routing events to specific channels based on defined criteria. It enables the selective forwarding of events to different channels, allowing for customized handling and distribution of data within the Flume agent.

For in-depth analysis of Hadoop job performance, JProfiler is a tool that can be used to profile Java applications. It provides detailed insights into the behavior and performance of Java code, helping developers optimize their Hadoop jobs for better efficiency.

The initial step in setting up a Hadoop cluster is to install the Hadoop software on all nodes. This involves downloading the Hadoop distribution, configuring environmental variables, and ensuring that the software is present on each machine in the cluster.

The RegionServer in HBase is responsible for storage and retrieval operations. It manages the actual data blocks, handling read and write requests, and communicates with the HBase Master to perform various tasks such as load balancing and failover.

Advanced Big Data analytics often employ Machine Learning techniques for predictive modeling and analysis. Machine Learning algorithms enable systems to learn and make predictions or decisions based on data patterns, contributing to advanced analytics in Big Data applications.

In HBase, the RowKey column is used to uniquely identify each row in a table. It serves as the primary key and is crucial for efficient data retrieval in HBase tables.

In HiveQL, the EXPLAIN command is used to show the query execution plan. It provides insights into how Hive intends to execute the given query, including the sequence of tasks and operations involved. Analyzing the execution plan helps optimize queries for better performance.

Data Serialization in Hadoop is crucial for optimizing read/write operations on large datasets. Serialization is the process of converting complex data structures into a format that can be easily transmitted or stored. In Hadoop, this optimization helps in efficient data transfer and storage.

In Flume, the Channel Selector mechanism allows for dynamic data routing and transformation. It helps in directing incoming data to different channels based on specified criteria, enabling flexibility in data processing and handling.

The NameNode in Hadoop is responsible for metadata management, storing information about the location and health of data blocks. It doesn't store the actual data but keeps track of where data is stored across the cluster. This metadata is crucial for the proper functioning of the Hadoop Distributed File System (HDFS).