Section 4: Players & Officials
Each team may have 18 players on the playing surface at any one time, with no more than four interchange players (Law 5.1). Variation of that number is provided for separately (Law 5.2). Traditional playing positions are conventional team structures rather than requirements of the Laws.
Umpires are governed by Law 8, covering their appointment and replacement (Law 8.1) and their duties (Law 8.2). Team officials and the team runner are dealt with separately (Law 6).
The choice of goal and the commencement of play, including the pre-match procedure between captains, are governed by Law 12 (Law 12.1 and Law 12.2). Timekeeping duties sit with Law 10.2.