In reply to Jaygyana:
uvm_event, uvm_queue, and uvm_pool are class wrappers arounds SystemVerilog events, queues, and associative arrays (Don’t ask me why they called it a ‘pool’). As class objects, they are easier to pass around your testbench environment consistently. The UVM has a lot of feature-creep; you probably won’t ever need all of the methods in the wrappers.