Who:
Chanty – Mid-19th century Anglo-American blue water sailors, typically clippers, windjammers, 'lime juicers' &c.
Maritime Work Song – Mariners.

What
Shanty – Excludes more tasks and functions than it includes.
MWS – Yes.

When
Chanty – Second half of 19th century, approx. 50 years.
MWS – Prehistory to present day. +2.400 yrs.

Where
Shanty – Wherever Anglo-American merchantmen sailed.
MWS – Wherever there was a maritime.

Why
Chanty – Timing and choreography.
MWS – Timing and choreography +training, enhortation, exhortation, command & control, navigation, piloting, &c &c &c.