Hello,
As your question is about the reinforcement details in footing, the vertically put L shaped or C shaped spacers between two horizontal rufts of reinforcements are known as Chairs.Chairs are provided to keep the top reinforcement in place and maintain proper spacing between top and bottom reinforcement.

L is development length.  the stress upon the reinforcement depends upon the load intensity. stress from reinforcements should be transferred to column. to make this happen we need an anchor of certain length to support it. it is the L you have asked.  it is used in civil engineering.

i hope it helps you.