Who can explain to me the straight-line scheduling, special-line scheduling, direct passengers and group tours of travel agencies? How do they operate during the trip?

For example, a travel agency in Qingdao is responsible for designing the tourist routes in Qingdao, and the special line planning is to design the routes in the peninsula or Shandong, and then notify the travel agencies in other places. This is the so-called peer sales. This foreign travel agency thinks this route is good, so it collects guests who want to go to Qingdao. This is the so-called direct customer sales. When a certain number of guests arrive and form a team, they will be sent to Qingdao. This foreign travel agency is called package travel agency, and Qingdao travel agency is called land agency.