The build tab is where you build and customize your workflow, there are multiple functionalities implemented here:
Dataset view where you can explore your training data.
Cleaning view, where you can set up cleaning filters to clean your data.
Splitting view, where you can split your texts into smaller snippets of text.
Models view, where you can add text analysis models including, sentiment, topics, subtopics, keywords and extraction.
Deploy view, where you can deploy your latest changes into production.