Vocabulary: numeral system where "||" represents "2"

Question

A useful system in some contexts where are you counting things is writing

1 as |

2 as ||

3 as |||

.

.

.

11 as |||| |||| |

Example of usefulness is keeping track of the number of cars that pass over a bridge.

What is the system called?

Answer 1

This system is called tally marks.