I am flying on March 16 from Barbados to Toronto on a Westjet Boeing 737-800 also referred to as an aircraft type 73H on my ticket. Is this a different plane from the Boeing 737 MAX 8, grounded by several countries?
They are different, yes. The 73H is not the Max 8. The 73H is an -800 with winglets. The -800 has been in service since 1998, with 4,991 deliveries as of February 28, 2019.
73H - Boeing 737-800 with winglets (8th letter of the alphabet)
The Max 8's IATA code you'd find on a ticket is 7M8.
For visual identification, see: Is this a 737-800 or 737 MAX 8?