Glue laminated timber can be produced straight or curved. For most columns, straight timber is used. Camber is often built into beams to reduce the visual effect of deflection under load.
The camber does not reduce the overall deflection. In cases where beam designs are governed by long term deflections from dead load, precambered beams may be of a smaller, more economical size than non-precambered beams because the deflection due to dead loads is accounted for by camber.
However, it should always be verified that the total long term vertical movement of a laminated beam is acceptable for the joints between the beam and other parts of the building.
Some manufacturers use a moderate "Standard Camber" on all their beams.
Reference: Timber Datafile P8 – Glue Laminated Timber of the NAFI Timber Manual