Getsul(ma)s are novices, holding 36 precepts. In Sanskrit they are called sramanera/sramanerika.
Other than in other traditions, it is not a probation, rather it is already an ordination for the entire life.
The essence of all vows lies in renunciation. It is a kind of renunciation that deprives our negative tendencies and emotions of their basis to further develop. We decide to give up all actions that will become the cause for negative activities because they are the basis for all disturbing emotions and of suffering – for ourselves as well as for others.
In this way the chain of unvirtuous habits is being cut and space for virtue evolves from it. The basis for spiritual development is being created which becomes the cause of joy, benefit for oneself and all sentient beings and hence for peace.