The meaning of holiday [Hagh] is pilgrimage to Yerushalayim from the villages and the cities and the tent camps surrounding Yerushalayim, in fulfillment of the biblical ordinances... This is as it is written, "all your males shall appear before YHWH your God" (Devarim 16.16).
The word holiday also refers to the circumambulation of the sanctuary. This is derived from the following: "They went around in circles [yahoggu] and staggered like a drunken man" (Tehilim 107.27), "he walks in the circuit of heaven" (Iyov 22.14), and "He sits above the circuit of the earth" (Yishiyahu 40.22). This meaning of holiday agrees with the expression, "I will walk around your altar, YHWH" (Tehilim 26.6). Pilgrimage includes the offering of sacrifices.
Hol HaMo‘ed - Intermediate Days of a Holiday
We say that these days, also, are designated as holidays and holy convocations, since they come under the statement, "These are the holidays of YHWH, holy convocations" (Wayyiqra’ 23:4), which forms the preamble to all the holidays. They are also comprised in the statement, "These are the holidays of YHWH which you shall proclaim to be holy convocations" (Wayyiqra’ 23:37).
We are forbidden on these days to engage in gainful occupations, commerce, and trades, except on the extend that we are compelled to, in order to provide for our livelihood, and to prevent danger to life. This applies, for example, to the irrigation of fields and gardens. Likewise, we may prepare medications and do bloodletting and other things required in the treatment of diseases. We may also bury the dead and do all things necessary for human safety. We may press fruit which would otherwise dry out, gather fruits which might spoil and sell and receive payment for them. We may store our crops in storehouses and remove flax from the vats in which it is soaking when there is danger of its rotting. We may remove wool from the dyeing vats before the becomes damaged. In general we may do everything that is urgent and cannot be neglected when failure to do so may cause harm. We may not engage in other worldly endeavors, this includes contracting or consummating a marriage, unless it be the case of remarrying a divorced wife.