There are TWO types of sequencers:

uvm_sequencer #(REQ, RSP) :

When the DRIVER initiates new requests for sequences, the sequencer selects a sequence from a list of available sequences to produce and deliver the next item to execute. In order to do this, this type of sequencer is USUALLY connected to a driver uvm_driver #(REQ, RSP).

uvm_push_sequencer #(REQ, RSP) :

The sequencer PUSHES new sequence items to the driver, but the driver has the ability to block the item flow when it’s not ready to accept any new transactions. This type of sequencer is connected to a driver of type uvm_push_driver # (REQ, RSP).

There are two types of sequencers:

uvm_sequencer #(REQ, RSP) :

When the driver initiates new requests for sequences, the sequencer selects a sequence from a list of available sequences to produce and deliver the next item to execute. In order to do this, this type of sequencer is usually connected to a driver uvm_driver #(REQ, RSP).

uvm_push_sequencer #(REQ, RSP) :

The sequencer pushes new sequence items to the driver, but the driver has the ability to block the item flow when it’s not ready to accept any new transactions. This type of sequencer is connected to a driver of type uvm_push_driver # (REQ, RSP).