FDA stands for Food and Drug Administration. This is a federal US agency which is responsible for the promotion and protection of public health. Pharmaceutical drugs, food substances and related stuff are all under the supervision of the FDA. You may check the Wikipedia page in order to familiarize yourself with all the responsibilities of the Food and Drug Administration of the US.
On this website, while we write about any product, we will make sure we state whether the said product meets FDA standards or not. In most cases however, most herbal supplements (the bulk of which we write about here) do not fall under regulations of the agency.
Note: Each country has its own version of this agency. Please make sure you are familiar with the ones that are closely related to you.