diff --git a/lz4diff/lz4diff_format.h b/lz4diff/lz4diff_format.h
index 5b5ce40..9875c12 100644
--- a/lz4diff/lz4diff_format.h
+++ b/lz4diff/lz4diff_format.h
@@ -58,8 +58,12 @@
 };
 
 struct CompressedFile {
+  // Extents in this array should be in range [0, file_size]. It represents
+  // which bytes inside this file are compressed. Useful for compressed file
+  // systems like EROFS.
   std::vector<CompressedBlock> blocks;
   CompressionAlgorithm algo;
+  // Whether the EROFS zero padding feature is enabled
   bool zero_padding_enabled{};
 };