Add dataset structure

README.md

@@ -61,6 +61,10 @@ print(next(iter(dataset))) #TODO: add int ids?
 TODO: How to use in a fondant pipeline?
 
 ## Dataset Structure
+### Data Instances
+Each data instance corresponds to one image. The URL of the image is in the `image_url` feature, and other features (`alt_text`, `webpage_url`, etc) provide some metadata. Note that images have been deduplicated only based on their URLs and not embeddings.
+
+### Data Fields
 - `image_url` (string): image url to download the image
 - `alt_text` (string): alternative text of the image
 - `webpage_url` (string): webpage source of the image
@@ -68,8 +72,14 @@ TODO: How to use in a fondant pipeline?
 - `license_location` (string): location of the license on the webpage
 - `surt_url` (string): sort friendly image url with top level domain as the prefix
 
+## Data Splits
+The dataset has no splits and all data is loaded as a [TODO: check split name - train?] split by default. If you want to setup a custom train-test split beware that the dataset may contain duplicates which can cause leakage into the test split.
+
+
 ## Dataset Creation
 ### Curation Rationale
+[TODO: insert intro from FAQ doc]
+
 ### Source Data
 #### Initial Data Collection and Normalization
 ##### License detection