Odds and probability are both used to express the likelihood of an event occurring in the context of gambling. Probability is expressed as a percentage chance, while odds can be presented in a few different formats, such as a decimal, fraction, or moneyline.
FanDuel offers much better odds on sporting events and does so with regularity. DraftKings also has competitive odds, but not to the degree that FanDuel does. FanDuel also has more bet types within each market, but DraftKings excels in every other area mentioned.