Joshua is dividing the land in which the rest of the tribes must have and he decides to send out three men from each of the seven tribes that remain to search out the land and bring back a report for him to decide which tribes gets from the reports.
When you are moving to a new place you must first search out the land that you are seeking to move into before you move. In order to know what you seek there has to be research done before hand. Moving is not done on a whim, you have to know what the people are like, the schools, work force, is the crime rate high and so forth.
