Admissibility is one of the concept of evidence.
Admissibility is the questions of law which is decide by the judges.
Admissible evidence means that the evidence can be properly admitted / received by the court in term of law.
Before establishing admissibility, the evidence must be relevant.
Irrelevant evidence is associated with inadmissible evidence.
As as conclusion, evidence must be relevant to be admissible.
However, certain rules of law of evidence will impose prohibition / restriction to the reception of certain type of evidence which is relevant. This action falls under the exclusionary rules.
Exclusionary rules focus on the attempt made to exclude evidence based on the court consideration.
For instance, in the case of rule against hearsay.
In this case, the court prohibit the reception of evidence based on the statement made by another person on another occasion and the purpose of adducing such evidence is to persuade the court to accept the truth of the statement made.