Reason #8,409: Your yard is on fire.

See, that’s what the hyphen there does. It indicates that the adjective ‘burning’ modifies ‘yard’, as the two are connected. If there wasn’t a hyphen there, ‘burning’ would modify ‘trainer’. So the trainer would be on fire in that case.

Neither of these scenarios makes a lot of sense to me. But if your yard is on fire, you might want to put it out. And if it’s not, you might want to look into some grammar lessons.