If you bought the premium Battle Pass , you have a chance of boosting the experience you get after each match.
For example in season 2, you get 50% Personal XP Boost instantly when buying the premium Battle Pass. Then you get 10% Personal XP Boost at tiers 2, 16, 30, 44, 68, 65, for a total of 110% XP Boost. So for example in a match in Season 2 let's say you get a total of 100 experience from Survival Time, Placement, and Kills. Your 110% experience bonus (assuming tier 65) would add another extra 110 experience, for a total of 210 experience (100 base + 110 from Battle Pass Bonus)