Load Lines (or Plimsoll Lines) are markings on the side of ships (amidships) which show the maximum limit of cargo a ship can load. They give different limits based on temperatures of water and salinity, as per the above diagram.
The logo on the left is the classification society marking. It indicates the ship's classification society by two letters, LR (for Lloyd's Register) or NV (for De Norsk Veritas) for example.
The lines can vary from the standard format on the basis of the ship's trading area and class. The standard format is as per the above diagram but some other examples are below.