Update model description

README.md

@@ -19,7 +19,9 @@ It achieves the following results on the evaluation set:
 
 ## Model description
 
-More information needed
+GPT2 is a large transformer-based language model. It is built using transformer decoder blocks. BERT, on the other hand, uses transformer encoder blocks. It adds Layer normalisation to the input of each sub-block, similar to a pre-activation residual networks and an additional layer normalisation.  
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+Paper link : [Language Models are Unsupervised Multitask Learners](https://d4mucfpksywv.cloudfront.net/better-language-models/language-models.pdf) 
 
 ## Intended uses & limitations