How a house is built
Attic room or storage
A trussed rafter spans like a rafter pair but uses webs. A raised heel leaves room for insulation at the eaves.
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A common truss has webs that fill the attic, which is fine until someone wants storage or a deep insulation blanket at the wall. A raised heel lifts the top chord at the eaves so the insulation can keep its depth where the roof meets the wall. An attic truss leaves a clear middle for a room and carries the loads in the webs at the sides.
Site-built rafters are assembled on site. A conventional ridge-board roof uses ties to resist outward thrust; a designed structural ridge-beam roof uses a different support arrangement. Trussed rafters arrive designed as units. Neither is drawn inside this roof. The shape of the house could be built either way.