When you need to categorize tasks or add keywords to them, you can use tags. How does it work in Bitrix24: first you add tags to the task form, then you can use filter above the tasks to find tasks with particular keyword (tag).
How to add tags to Bitrix24 tasks
Open new task form to create a new task (or open existing task for editing) & navigate to More section below the form, the Tag option is listed there among the available options, click on it to unroll:
Go to Tag section and click on Add to open tags form. Here you can either add new tags or select one of those you've added before. You can add\select multiple tags for one task.
How to filter tasks by tags
Once the tags have been added, you can filter your tasks by tags. First, click on Filter to open it & click on Add field & select Tag field in order to add it to the filter:
Now, when Tag field is available inside the filter, you can enter tag name there:
All tasks with this tag will be shown under the filter after filter tag condition is applied:
You can open the task to check it's tag - it will be shown in the right side widget: