A lidmaat is a member of a church. In earlier time, when you moved to another town, you would register at the local church. For that you would bring a paper stating you were a good person (read member of a church). Then you would register at that church.
Compare this to the current Civil registration.
A 'gevormde' (note the spelling) is someone that registered at a new church, so probably without the paperslip or really at a new church.
So for this source it is the registration of the two people at the church of Gelselaar in Gelderland, Nederland.
