Designed to be the successor of the core profile module, which is deprecated for Drupal 7. In contrast to the deprecated module this module provides a new, fieldable 'profile' entity - leverage the power of fields!
As described in the documentation Drupal 7 allows adding fields to user account pages - what serves as simple way for building user profiles. The main differences between that and profile2 are:
With profile2 user account settings and user profiles are conceptually different things, e.g. with the "Profile pages" module enabled users get two separate menu links "My account" and "My profile".
Profile2 allows for creating multiple profile types, which may be assigned to roles via permissions (e.g. a general profile + a customer profile)
Profile2 supports private profile fields, which are only shown to the user owning the profile and to administrators.
Multi-path autocomplete (formely known as Menu path autocomplete) changes some input field for entering paths to an autocomplete text field so users do not need to know the internal system path but simply can enter the title of the page to link to.
Taxonomy Single Tag improves core's taxonomy autocomplete by allowing commas to be used as part of the taxonomy term. To do this, TST limits autocomplete taxonomy fields to a single term.