A man with ski poles and a large camping backpack treks through the snow.
A man is trekking through the snow with ski poles.
"A man with ski poles and a large camping backpack treks through the snow" is a rephrase of "A man is trekking through the snow with ski poles."
Trekking through the show and treks through the snow both imply that the man doing this right now.
trekking is a rephrasing of treks