With Moneyline wagering, you are betting on which team will win, regardless of the score margin. Favourites have negative odds (for example, -150: bet $150 to win $100). Underdogs have positive odds (for example, +130: bet $100 to win $130).
Spread betting is designed to level the playing field from a betting perspective.
For example: the Dallas Stars may be considered a 1.5 goal favourite against the Toronto Maple Leafs. If you bet on the Stars, they must win by 2 or more goals to cover the spread. If you bet on the Maple Leafs, they can lose by 1 goal or win the match for it to cover the spread.