improve phrasing in overview.md

Author: kspalaiologos

doc/overview.md

@@ -1,8 +1,9 @@
 # BZip3 Format Documentation
 
 BZip3 is a modern compression format designed for high compression ratios while maintaining
-reasonable decompression speeds. It targets the same category/weight as LZMA and BZip2; as opposed
-to the speedy LZ based formats like ZStandard
+reasonable decompression speeds. It is intended to provide similar compression ratio and
+performance to LZMA and BZip2; as opposed to faster Lempel-Ziv codecs that usually offer worse
+compression ratio like ZStandard or LZ4.
 
 This documentation covers the technical specifications of the BZip3 format.
 
@@ -13,15 +14,17 @@ This documentation covers the technical specifications of the BZip3 format.
 - Memory usage of ~(6 x block size), both compression and decompression
 - Little-endian encoding for integers
 - Embedded CRC32 checksums for data integrity
-- Combines LZP, RLE followed by Burrows-Wheeler transform and arithmetic coding.
+- Combines LZP, RLE followed by Burrows-Wheeler transform and arithmetic coding coupled with
+  a statistical predictor.
 
 ## Format Overview
 
-BZip3 uses two main formats:
+BZip3 uses two main top-level formats:
 
 1. **File Format**: The standard format used by the command-line tool
 2. **Frame Format**: Used by the high-level API functions `bz3_compress` and `bz3_decompress`.
 
-These formats are the same, except the fact that the file format also contains a block count field.
+These formats are very similar: the file format is a superset of the frame format and thus also
+contains a block count field.
 
-See [bzip3_format.md](./bzip3_format.md) for the exact specification.
+See [bzip3_format.md](./bzip3_format.md) for more details.