First Article Approval is the process of approving the first products created from your new mold — sometimes this process will need repeating if your engineers find flaws with the design, mold dimensions, or you are not happy with the color or final material feel. Essentially, this step in the production process means you get the highest possible quality product that matches your requirements.
During First Article Approval engineers from your manufacturer will issue a report comparing your dimensional requirements and other such specifications with the results of the molded product. Any arising issues are generally addressed immediately, with the manufacturer working to get your product to the exact specifications you require.
Once you approve this first article, and are happy with the results, real production begins. Injection molding is an incredibly fast process, so once manufacturing begins in earnest you could see as many as 1 million parts delivered within 12 weeks.