Update prepare-for-submission.mdx

Made a few tweaks to the content. See https://docs.google.com/document/d/13JPa34xPXdWkrBk8gGQizw_V0cHunUFMJxtDJJgkx54/edit?usp=sharing for more details.

docs/learn/data-submitters/submission-guide/prepare-for-submission.mdx

@@ -12,10 +12,10 @@ In this step, you will prepare for data ingestion by organizing all required dat
 </Alert>
 
 ### AnVIL accepts two types of data 
-- **Genomic object files**   
-Genomic object files require minimal metadata, some of which is generated by the AnVIL (such as full paths to the files in AnVIL cloud storage).   
-- **Clinical data, phenotypes, and metadata**      
-Submitted in TSV format (see requirements below)
+- **Object files (large, unstructured data files)**   
+Object files include genomic and other omics data as well as image files. Object files require minimal metadata, some of which is generated by the AnVIL (such as full paths to the files in AnVIL cloud storage).   
+**Phenotypes and metadata**      
+Clinical and phenotypic data as well as object file metadata will be submitted in TSV/TXT format (see requirements below).
 
 **Most studies are submitting both.**