Thanks noobmaster for helping me with this.
But if the queue and the buffer are separate memory spaces for packets, more questions are raised.
1: When a queue is said to be half full (leading to say.. Random Early Discarded packets) or completely full (leading to Tail Dropped packets), what's the state of the buffer?
2: When is a packet queued and when is it buffered?
3: I see mention of buffer size a lot. But how long is a queue?
4: At what point are there several packets in both the buffer and the queue?