Read data from NFC tag (IsoDep)

I am newbie in Android NFC API.

Currently, I have a NFC tag, I am making an Android app to read data from it. My simple App is launched when my phone get closer enough to the NFC Tag. But I have no idea how to read the data inside the NFC Tag. The tag uses IsoDep technology.

My current code:

@Override
protected void onResume (){
    super.onResume();

    Intent intent = getIntent();
    Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);

    IsoDep isoDep = IsoDep.get(tag);
   
    // How to read data from IsoDep instance?

I googled on internet, I notice people are sending commands to IsoDep to get response from NFC Tag, I suppose from the response, we can parse the data in the tag, I saw people doing this:

//What is the 'command' ? How to define the command?
//e.g.:
byte command = (byte) 0x6A
isoDep.transceive(command)

But, the command is just a byte, as a newbie, it is too difficult to understand what is happening. I have no idea how to define the command to read data? Anyone can explain to me? or is there a document I can learn about the command?

Generally, I need some guidance on how to define commands & how to parse data from response, I would like to read the data stored in the Tag & show the data in String format in UI element (e.g. TextView).

AND

I have no problem with those configurations(e.g. AnroidManifest.xml), please don't guide me on how to configure :)