Many 3rd party apps attempt to gain approval to access your O365 data. Many have good intentions while many others want to use your data for undesirable purposes. You may encounter this in a screen which asks you to gain "Admin Approval" to allow a 3rd party application to have direct access to your data.
Due to the risk in allowing 3rd party applications to access LETU users' data, we follow MS recommendations to disable 3rd party applications access to LETU O365 data (including Email, Calendar, OneDrive, etc) until those applications are carefully vetted by LETU.
LETU generally reviews O365 3rd party applications for possible approval only if they are directly related to software LETU owns which has gone through our vendor security guidelines process. For the protection of all LETU users and data, other 3rd party applications will generally not be permitted access to O365 data.
For an example of the type of risk introduced by approving 3rd party Apps without fully understanding what they do in detail how they are programmed - see this article on how doing so can eliminate the security benefits you enjoy from multifactor authentication (MFA).