Odds written out as 5/1, 5-1, or 5-to-1, indicate fractional odds notation. The 5/1 odds here are just an example, as 10/1, 9-4, 7-to-2 and any other odds displayed in this fashion represent fractional odds.
A winning bet made at 5-to-1 odds means you win $5 for every $1 bet. For example, a $100 bet made at 5-to-1 odds pays $500 in profit ($100 x 5). This bet would return $600 total ($500 profit plus the return of the original $100 bet).
A 5-to-1 fractional odds bet is equivalent to +500 moneyline odds, or 6.00 decimal odds.