Explain how baseURI is used for building the tokenURI (#2679)

contracts/token/ERC721/ERC721.sol

@@ -98,8 +98,9 @@ contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
     }
 
     /**
-     * @dev Base URI for computing {tokenURI}. Empty by default, can be overriden
-     * in child contracts.
+     * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
+     * token will be the concatenation of the `baseURI` and the `tokenId`. Empty 
+     * by default, can be overriden in child contracts.
      */
     function _baseURI() internal view virtual returns (string memory) {
         return "";