I've been learning about COUNT function in SQL. They give me an example but I don't really understand the COUNT syntax mean. Can you please explain it specifically ? This is the code

SELECT
  usertype
  CONCAT (start_station_name," to ", end_station_name) AS route, 
  COUNT (*) as num_trips,
  ROUND(AVG(cast(tripduration as int64)/60),2) AS duration 
FROM 
  `bigquery-public-data.new_york.citibike_trips`
GROUP BY
  start_station_name, end_station_name, usertype 
ORDER BY 
  num_trips DESC 
LIMIT 10