Sometimes when a team/player is so heavily favoured then there will usually be a Handicap placed on it (sometimes shortened to H/C) this means that the team less favoured to win are given an advantage to help balance out the result and (hopefully) make the betting more interesting.
Team A (-1)
Team B (+1)
In layman terms, this means at the start of the match/race Team B has a 1-0 advantage automatically.
Team A can only win the bet if they win by 2 or more goals/points.
Team B can win the bet if they either win or draw (as they already have the 1-0 advantage at the start of the match/race)
Handicap draw will win if Team A wins by just 1 goal/point.
Sometimes in the bookies you will see handicaps of -3.5, this means that the team who are the favourites will have to win by 4 or more.
Team A (-3.5)
Team B (+3.5)
Team A can only win if they win by 4 or more goals/points.
Team B can win if they draw or are up to 3 goals/points behind
As .5 in sports is very rare and only used in a minority of sports these type of handicaps never have a draw option.
In some cup competitions (mainly in soccer (US), football (everywhere else)) where extra time can be involved, if there is an option for a draw then that means only the score up to the regulation time counts. Extra time does not factor in these games. If, however there is no option for a draw then the winner is the one who wins the game at the final whistle(whether it be in regulation time or extra time).