The pivotal position in the team. In NFL terms: think of the flyhalf as both the Quarterback on attack and the Middle Linebacker on defense. Key decision makers (with scrumhalf). Decides whether to pass, kick, or run depending on the strategic position of the team, and the defensive positioning and alignment of the opposing team. On defense, they control the speed of the line and count numbers constantly to match the attack, and communicate instructions and commands constantly to his fellow back-line players.
The flyhalf should be exceptionally skilled with the ball. They should aim for fast and accurate delivery from either hand even when under pressure from the defense. The flyhalf should be able to kick off either foot in different ways. These include chips, grubbers, drop goals and bombs. Owning these skills forces the defense to respect these attacking options and can create space for the attack to maneuver. Very often the flyhalf is also the player to kick for goal (conversions and penalty kicks).
On attack, the flyhalf sets the depth of the attacking line. How far they’re able to stand away from the breakdown or setpiece will depend on the skill of the scrumhalf. How far they’re able to stand away from the defensive line will depend on their own skill. The closer the flyhalf can play to the defensive line, the more skilled they are. Playing close to the defensive line is desirable as it forces the defense to hold still rather than moving forward in unison.
The defensive line gets their speed and spacing from the flyhalf. You are the BOSS. Too narrow or wide and the attack will have gaps to exploit. Too slow and you and your defenders will be caught flat footed in contact. The flyhalf channel at breakdowns is almost always the most direct route to the tryline, therefore, their tackles are highly important.