update README

README.md

 # nerfacc
 
-This is a tiny tootlbox for fast NeRF rendering.
-
+This is a **tiny** tootlbox for **accelerating** NeRF training & rendering using PyTorch CUDA extensions. Plug-and-play for most of the NeRFs!
 
 ## Instant-NGP example
 
@@ -9,7 +8,6 @@ This is a tiny tootlbox for fast NeRF rendering.
 python examples/trainval.py
 ```
 
-
 ## Performance Reference
 
 Tested with the default settings on the Lego dataset.