Mongoid where vs find when using id as criteria

Question

when using document's id as the only criteria in my query what's the difference between:

Board.only(:_id).find(params[:board_id])

and

Board.where(_id: params[:board_id]).only(:_id)

the only thing i've noticed is that printing the result as json when using where it encloses the result in square brackets

Answer 1

find returns one document.

where returns an array of documents that match the criteria.

Answer 2

To add to Kyle's answer:

If matching record is not found: find throws exception, where returns empty enumerable.