Hare Krsna !
Om ajnana timirandhasya jnananjana salakaya Caksur-unmilitam yena tasmai sri-guruve namah
nama om visnu-padaya radhikayah priyatmane sri-srimad-bhaktivedanta narayana iti namine
Ekadasi is a sacred day 11 days after the full moon or new moon.
Fasting from grains on that day is beneficial for health, but mostly for spiritual development and purification.