Oil seals are designed for sealing shafts and spindles.
Providing long-lasting sealing efficiency, they consist of a rubber sealing lip, metal case and a spiralled tensioning spring. Available with or without external dust lip, they are self-retained in an open groove to ISO 6194 and DIN 3760. Versions come without the spring for grease applications, for use as a scraper or for helical movement.
Oil Seals are used to exclude water, Dirt, Dust or any other substances from mechanical equipment whilst maintaining lubrication.
Coming to Answer
Pump is Mechanical equipment
Motor is its driver.
Both shafts are connected with coupling
Shafts rotated with bearings with lubricants, from their respective chambers.
In chambers oil or grease is filled to lubricate shafts. At shaft and chamber edges there will be an oil seal holding neck.
There oil seals are fixed to prevent leakage and Shaft damage.