explain methods

README.md

@@ -33,6 +33,8 @@ const tags = {
 ```
 
 ### Write tags to file
+If you have an existing file/buffer (e.g. an mp3 file) you can use the write method to write your tags into it. It will remove existing tags and add yours.
+
 ```javascript
 const success = NodeID3.write(tags, filepath) // Returns true/Error
 // async version
@@ -47,7 +49,8 @@ NodeID3.write(tags, file, function(err, buffer) {  })
 ```
 
 ### Update existing tags of file or buffer
-This will write new/changed values but keep all others
+The update method works like the write method but will keep or overwrite existing tags instead of removing them.
+
 ```javascript
 const success = NodeID3.update(tags, filepath) //  Returns true/Error
 const success = NodeID3.update(tags, filebuffer) //  Returns Buffer
@@ -67,6 +70,7 @@ NodeID3.update(tags, filebuffer, options, function(err, buffer) {  })
 ```
 
 ### Create tags as buffer
+The create method will return a buffer of your ID3-Tag. You can use it to e.g. write it into a file yourself instead of using the write method.
 ```javascript
 const success = NodeID3.create(tags) // Returns ID3-Tag Buffer
 // async version