When you are getting a sports betting deposit bonus from a bookmaker, this means that you are getting a certain percentage in bonus money in relation to the amount you deposit. For example, a very common betting bonus is 100%, where your deposit will be doubled. At FansBet you can even get a higher bonus!
Say you deposit £50, which will mean that with a 100% bonus you will get £50+£50 in bonus money = £100 to play with. A 50% bonus will net you €25 in bonus money, a 200% bonus will triple your money etc. These bonuses will often have some kind of wagering requirement for the bonus money, ranging from 4-10x before the bonus money can be withdrawn.