What is the concept of error bars in barplots in seaborn library?
It appears that even if you don't enter ci argument, it's set to 95 by default in barplot method, which gives you those error bars. If you don't want them, set ci = None while plotting. The bar is the confidence interval for the variable as the library describes, i.e. it's interval where the 95 % of your variable lies in, which is estimated by bootstrapping.