The information submitted regarding the purpose and conditions of the intended stay was not reliable.
This means the stated objective of your visit required supporting documentation, and the supporting documentation you provided relied upon assumptions that were not visibly certain or were, in some other way, doubtful. Common examples are
the resources needed to accomplish the visit are wholly
disproportionate to the applicant's income and capacity (for example
a visit requiring half the applicant's annual income)
the applicant showed sufficient resources, but it is not clear that
the resources are actually available to the applicant or that the
applicant intends to use the resources as stated (for example, a
funds parking arrangement).
the applicant did not satisfactorily explain why a visit to that
particular country is being arranged at this particular point in
time. This is especially true for first-time applicants because
while they are willing to accept that everyone must begin travelling
at some point, a first-time applicant needs to be careful to assure that
these conditions are adequately and transparently reconciled.
the applicant has not provided realistic or concrete plans. This
could suggest a secondary motivation for seeking a visa and hence the
purpose is 'not reliable'.
the stated purpose is not consistent with the applicant's life-style
or interests. For example someone with no prior involvement in
archaeology wanting to participate in a digging project; or someone
wanting to take a language course with no ostensible reason for doing
Their intention to travel outside the territory of the Member States before the expiration of the visa could not be determined.
This means that the applicant did not successfully mitigate their performance risk. Common examples of this are...
the applicant does not have a history of travel to countries that
require visas and therefore the decision-maker cannot rely upon
performance history to mitigate risk.
the applicant does not show an economic standing that is
significantly better than the target country's income support,
housing benefit, and comparable welfare programme.
the applicant does not show strong and permanent ties to his own
economy such that his presence is needed in his own country in order
to maintain a viable economic standing (or more simply, a
satisfactory employment history in a reputable job).
the applicant does not show strong and permanent ties to his family
or community such that the decision-maker can see bonds and
commitments that would compel the applicant to return to his own
This is not an exhaustive list and your question did not include substantive detail about what was stated in your application, but these items do show the kinds of criteria that decision-makers use to select which grounds for refusal are relevant to your application.