Confused with intra-thread and inter-tread in the UVM primer

in the uvm primer chapter 16
in the case of one -tread ( intra-thread ) use analysis_port as a solution. connect monitor and scb
in chapter 17 inter-tread
use ports and TLM_fifo as a solution to handle the case of inter-tread,
connect the driver and tester(like sequencer /sequence)

why the case of connect monitor and scb is intra-thread?
is monitor / scb /driver /sequencer in one-tread?