Summarise in own words:

Article 15
Prosecutor
1.The Prosecutor may initiate investigations proprio motu on the basis of information on crimes within the jurisdiction of the Court.
2. The Prosecutor shall analyse the seriousness of the information received. For this purpose, he or she may seek additional information from States, organs of the United Nations, intergovernmental or non governmental organizations, or other reliable sources that he or she deems appropriate, and may receive written or oral testimony at the seat of the Court.
3. If the Prosecutor concludes that there is a reasonable basis to proceed with an investigation, he or she shall submit to the Pre-Trial Chamber a request for authorization of an investigation, together with any supporting material collected. Victims may make representations to the Pre-Trial Chamber, in accordance with the Rules of Procedure and Evidence.
4. If the Pre-Trial Chamber, upon examination of the request and the supporting material, considers that there is a reasonable basis to proceed with an investigation, and that the case appears to fall within the jurisdiction of the Court, it shall authorize the commencement of the investigation, without prejudice to subsequent determinations by the Court with regard to the jurisdiction and admissibility of a case.

The Prosecutor of the International Criminal Court has the authority to start investigations on their own based on information about crimes within the Court's jurisdiction. They can gather additional information from various sources and, if they believe there is enough evidence to proceed, they can request authorization from the Pre-Trial Chamber to start an investigation. The Pre-Trial Chamber will then determine if there is enough evidence to proceed with the investigation, keeping in mind the Court's jurisdiction and the admissibility of the case. Throughout this process, victims have the opportunity to make representations to the Pre-Trial Chamber.