Complex sentence: The block chain provides only a certain level of anonymity, hence also called "pseudo-anonymity"; it identifies receivers by Bitcoin addresses, not individuals' names, but racking the flow of bitcoins can give clues as to who owns them.
Split into simpler sentences: The block chain provides only a certain level of anonymity; it identifies receivers by Bitcoin addresses, not individuals' names. Tracking the flow of bitcoins can give clues as to who owns them.