Wiktionary
n. A loop made up of complex knots used by members of the Eastern Orthodox and Eastern Catholic churches to count the number of times they have prayed the Jesus Prayer.
Wikipedia
A prayer rope ( Greek: - komboskini; Russian: чётки - chotki (most common term) or вервица - vervitsa (literal translation); Arabic - misbaha; Romanian: metanii / metanier; Macedonian and Serbian: бројаница - broyanitsa; Bulgarian: броеница - broyenitsa) is a loop made up of complex knots, usually out of wool or silk. Oriental Orthodox also use it but it is referred to as the mequetaria.
The prayer rope is part of the habit of Eastern Orthodox and Greek-Catholic monks and nuns and is employed by monastics (and sometimes by others) to count the number of times one has prayed the Jesus Prayer or, occasionally, other prayers.