Here is a quick tutorial to describe the differences between: hail, graupel (soft hail / snow pellets), ice pellets (sleet) and freezing rain. Wikipedia puts it this way:
HAIL is a form of solid precipitation. It is distinct from ice pellets (American sleet), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. [...] Unlike other forms of water ice such as graupel, which is made of rime, and ice pellets, which are smaller and translucent, hailstones usually measure between 5 millimetres (0.2 in) and 15 centimetres (6 in) in diameter.
In more detail: https://en.wikipedia.org/wiki/Hail
GRAUPEL (from German language), also called SOFT HAIL or SNOW PELLETS, is precipitation that forms when supercooled water droplets are collected and freeze on falling snowflakes, forming 2–5 mm (0.08–0.20 in) balls of rime. Graupel is distinct from hail, small hail and ice pellets: the World Meteorological Organization defines small hail as snow pellets encapsulated by ice, a precipitation halfway between graupel and hail.
In more detail: https://en.wikipedia.org/wiki/Graupel
ICE PELLETS (American: SLEET) are rain drops that have frozen before they hit the ground. When they hit the ground, they bounce. Ice pellets are also called sleet and can be accompanied by freezing rain. In winter, precipitation usually begins falling out of a cloud as ice particles.
In more detail: https://en.wikipedia.org/wiki/Ice_pellets
FREEZING RAIN is the name given to rain precipitation that freezes on contact on surfaces maintained at temperature below freezing by the ambient air mass. Unlike sleet, a mixture of rain and snow, ice pellets, or hail, freezing rain is made entirely of liquid droplets. The raindrops become supercooled while passing through a sub-freezing layer of air hundreds of meters above the ground, and then freeze upon impact with any surface they encounter...
In more detail: https://en.wikipedia.org/wiki/Freezing_rain