When you see Read, this is Bedrock looking at the objects and fields in your system and gathering that information or values on those fields. It means that Bedrock Data is able to sync this data over to another system. In some cases, you can only Read data from an Object, it means this is a Read-Only type and you won't be able to Create or Update the data in this Object.
When you see Update in reference to an Object or a Field, this means that Bedrock Data will be able to change this data.
When you see Create this is always in reference to an Object type that Bedrock Data will be able to make new records for this object within the sync. This is often dependent upon the other system you are integrating with having a related object where the two objects can be mapped directly.