When standing with hand support at a high step the hips are flexed and the base of support is large in the A-P direction. In this position he is able to explore different ways of adjusting the feet and hands on the support surfaces (floor and step) to allow him to reach for toys.
In this series of video clips you see Will, 9 months 2 weeks, standing with support and reaching for and throwing a ball. The repeated reaching for the ball challenges his balance.
Once a typically developing infant has learned to balance and reach to the side, they will usually start to take a single step, and later multiple steps sideways when reaching for toys that is out of reach.
Infants just learning to stand really enjoy standing facing a family member or carer and grabbing onto clothing for support. 
This clip shows how max (17 months) explores stepping actions to establish effective equilibrium for standing and reaching. 
Once a typically developing infant has learned to balance and reach to the side, they will usually start to take a single step, and later multiple steps sideways when reaching for toys that is out of reach. 
Typically developing toddlers mostly fall without hurting themselves. This is because they have learned to flex their knees as they go down.