Text classification means assigning a class or category to a text, it is also known as tagging. One or more categories can be assigned to a particular text depending if you want to work with single or multilabel classification.
A machine learning classifier, learns to assign the corresponding category to a text by using mathematical models and algorithms that learn to associate a particular input (text) to the corresponding output (label). This is done automatically, the only thing that you have to do in MonkeyLearn if you want to create your custom text classifier, is to define your categories and upload text samples for each category. Then the algorithm will learn to do the classsifications by training over the examples that you provided. Text samples can be reviews, articles, emails, tweets, comments, any piece of text.
You can keep learning about classification the section about Custom Modules for Text Classification in our help center.