A tag allows you to characterize a task.
This can be a class of maintenance intervention (electrical, boilermaking, mechanical, etc.), a type of intervention (preventive, curative, improvement, etc.), a degree of urgency, a production stop, a security tag, and so on.
Tags are important because they allow you to get statistics on your maintenance interventions, or to filter a set of data.
There are no limits for the tags that can be added to a task.