Update README.md

Author: lemire

README.md

@@ -1,6 +1,10 @@
 # browserbase64
 
-This is an in-browser base64 benchmark.
+
+Base64 is a binary-to-text encoding scheme that converts arbitrary binary data (like images, files, or any sequence of bytes) into a safe, printable ASCII string using a 64-character alphabet (A–Z, a–z, 0–9, +, /).
+Browsers use it in JavaScript to embedding binary data directly in code or HTML or to transmitting binary data  as text.
+
+This is an in-browser base64 benchmark:
 
 - [Visit the benchmark](https://simdutf.github.io/browserbase64/html).