When Honorable court grants a bail on some condition it is called Interim Bail. Yes the interim bail can be extended and if the period of interim bail gets over and the accused person does not prays before the court for confirmation and/or continuation of the interim bail then the liberty granted under the interim bail is cancelled and the accused person be taken into custody or W/A will be issued against him.
When an application for the grant of bail is filed before a Court like Supreme Court or High Court, it requires documents from lower Courts or investigation agency like charge sheet, certified copies of documents, case diary etc to take decision. But the process to get these documents require time and the accused or convict has to remain in jail till the court gets hold of these documents and can decide on the bail plea. But accused or convict can apply for an interim bail to avoid jail for such period till higher court gets required documents from the lower court or investigating agency. Thus interim bail is a temporary bail for a period in which higher court can call documents required to make a final decision on the bail application in which court can either grant permanent bail, extent interim bail or even can reject bail application.