They are like any other reservist, they are what we so called in-and-out of the program. Which mean they are required to do service time once in a while, and then that responsibility is release.
They are trained in fighting, in fact, most of the reservist were the one that were deployed to Donbas and relieved for duty from regular rotation. They are more or less the same as regular troop, you just need some time to train them and equip them.
There are 3 type of Army Reservist in Ukraine.
Type 1 is the Reservist with 60 days training over 2 years, Type 2 is Reservist with 30 days training over 2 years and that made up the bulk of Current Reserve Force, there are a type 3, mobilisation reserve, that's basically everyone who can be drafted, will be drafted.