Matalot uses categories in order to let you organize your tasks into conceptually different groups. Categories have two main advantages:
You access your categories via the Categories tab. In this tab you'll get a list of all your categories, ordered by their relevance. The relevance of categories is determined based on their locations and their tasks. The category who's location is the closest and its tasks are the most important will be first.
The Categories tab gives you a high level look on your tasks. Usually, there's no need to go to this tab in order to see what you have to do. The Current and Uncompleted tabs are designed exactly for that. That being said, if you do wish to view tasks by category, you can simply select a given category from the Categories tab.
When you need to create a new category, there are two ways to do that: