Branched-chain amino acids, or BCAAs, are made up of three amino acids: leucine, isoleucine, and valine.
These amino acids can be found in dietary protein, such as meat or eggs, or taken in dietary supplements.
These foods contain all three BCAAs in one serving:
Chicken breast
Lean beef
Steak
Canned tuna
Wild salmon
Haddock
Trout
Turkey breast
Eggs (3)
Lowfat Greek yogurt (1 cup)
Branched-chain amino acids are most commonly used for their role in muscle building,
Thanks to them, training efficiency improves, signs of muscle fatigue and recovery time are reduced.
Supplements.
If your diet is lacking in protein, or you don't eat meat at all, then it is recommended to take BCAA supplements.
Also, if you like to exercise on an empty stomach, BCAA supplements are a good option.

Below I will provide information about the benefits of BCAA supplements that I found in foreign sources:
BCAA supplementation improves exercise performance
BCAA supplementation reduces fatigue and increases endurance
BCAA supplements may improve fat burning
BCAA supplements increase muscle mass
BCAA supplements may reduce pain
BCAA supplements may reduce muscle damage
BCAA supplements may increase short-term memory performance after exercise
BCAA supplements may reduce reaction time
BCAA supplements reduce perceived pain
BCAA supplements improve breathing
BCAA supplements do not affect heart rate
BCAA supplements may improve liver health
BCAA supplements may improve kidney health
BCAA supplements may prevent heart failure
BCAAs can increase energy
BCAAs may improve insulin resistance and diabetes
BCAA supplementation may improve sleep quality
Of course, like all supplements, BCAAs can have side effects, so always take them as directed by the manufacturer.
Sources:
https://www.livestrong.com/article/440616-branch-chain-amino-acid-benefits/
https://www.womenshealthmag.com/food/bcaa-benefits
https://www.selfhacked.com/blog/bcaas-health-benefits-bcaa/