add additional docs to etl Collector

crates/etl/src/lib.rs

@@ -30,9 +30,12 @@ use tempfile::{NamedTempFile, TempDir};
 /// An ETL (extract, transform, load) data collector.
 ///
 /// Data is pushed (extract) to the collector which internally flushes the data in a sorted
-/// (transform) manner to files of some specified capacity.
+/// (transform) manner to files of some specified capacity. the data can later be iterated over
+/// (load) in a sorted manner.
 ///
-/// The data can later be iterated over (load) in a sorted manner.
+/// Used mainly to insert data into `MDBX` in a sorted manner. This is important because performance
+/// and storage space degrades greatly if the data is inserted unsorted (eg. tables with hashes as keys.) as
+/// opposed to append & sorted insert. Some benchmarks can be found [here](https://github.com/paradigmxyz/reth/pull/1130#issuecomment-1418642755).
 #[derive(Debug)]
 pub struct Collector<K, V>
 where