This looks like peach leaf curl, a preventable fungal disease. This can cause some defoliation but not typically a significant problem. Spray liquid lime sulfur or another fungicide at bud break. It is too late for treatment this year. If there are not too many leaves affected, you can remove them and dispose of in the trash. Hand thin the peaches. See our web page on stone fruit diseases.  https://extension.umd.edu/resource/peach-and-cherry-diseases

Here is more on care of peaches, fertilizing, spray schedules, etc.  https://extension.umd.edu/resource/growing-selecting-planting-peach-and-cherry-trees

Marian