Labels (a.k.a. tags) are used for grouping multiple agents into one logical group. Use spaces between each label. For instance, 'regression java6' will assign the labels 'regression' and 'java6' to the node. If you have multiple Windows agents and you have jobs that require Windows, then you can configure all your Windows agents to have the label 'windows', then associated the job with the 'windows' label. This allows your job to run on any of your Windows agents but not anywhere else.