You will probably know that the notation for galvanic cell reads from left to right as anode || cathode, where || typically denotes a salt bridge.
Within each half cell, different phases are separated by |.
In your case, the anode is a platinum rod in an acidic solution under a hydrogen atmosphere. This is a Standard hydrogen electrode (SHE).
The cathode consists of a platinum rod which is contact with a layer of mercury and a layer of solid mercury(I) chloride. It is an aqueous cell with 1M KCl solution as the medium. This electrode is known as Saturated calomel electrode (SCE).
Both electrodes are used as reference electrodes.