Chol Hamoed (Hebrew: חול המועד) refers to the intermediate period of the festivals of Passover and Sukkot. The meaning of Chol Hamoed is the weekday of the Holiday.
These are the days sandwiched between the beginning and end holy days of both festivals.
Passover is celebrated for seven or eight days (In Israel it’s celebrated for 7 days). The first two days and last two days are full-fledged festival days, and the middle four days are named: Chol Hamoed.
On the full-fledged festival days of Passover, Jews are prohibited from creative work, just like Shabbat.
However, on Chol Hamoed, Jews are permitted to do many of these activities: use electricity, drive a car , cook etc. The religious Jews are try to avoid going to work, doing laundry and writing.
The special Mitzvahs of the festival are equally observed on Chol Hamoed. For example, Jews may not eat Chametz during Chol Hamoed of Passover. The days of Chol Hamoed also include the mitzvah to be joyous and celebrate.
There are special prayers and Torah readings in the Synagogue during Chol Hamoed, and in many communities men do not put on Tefillin.