Edit explanation comment

This change gives more clear meaning.

Author: youngminpark2559

bitcoin_transfer/private_key.md

@@ -6,8 +6,8 @@ Private keys are often represented in Base58Check called a **Bitcoin Secret** (a
 
 ```cs  
 Key privateKey = new Key(); // generate a random private key
-BitcoinSecret mainNetPrivateKey = privateKey.GetBitcoinSecret(Network.Main);  // get our private key for the mainnet
-BitcoinSecret testNetPrivateKey = privateKey.GetBitcoinSecret(Network.TestNet);  // get our private key for the testnet
+BitcoinSecret mainNetPrivateKey = privateKey.GetBitcoinSecret(Network.Main);  // generate our Bitcoin secret(also known as Wallet Import Format or simply WIF) from our private key for the mainnet
+BitcoinSecret testNetPrivateKey = privateKey.GetBitcoinSecret(Network.TestNet);  // generate our Bitcoin secret(also known as Wallet Import Format or simply WIF) from our private key for the testnet
 Console.WriteLine(mainNetPrivateKey); // L5B67zvrndS5c71EjkrTJZ99UaoVbMUAK58GKdQUfYCpAa6jypvn
 Console.WriteLine(testNetPrivateKey); // cVY5auviDh8LmYUW8AfafseD6p6uFoZrP7GjS3rzAerpRKE9Wmuz