What is technical meaning of point in time recovery? Please can I have a technical meaning of point in time recovery? Does it mean that given a backup file, we must be able to recover upto any point in time during the span of the time covered by the backup?

If so, then is it right to say only a transaction log backup will allow for this? Or is only full or differential backup sufficient? How about recovery models - is full recovery model a must? Or can it be bulk recovery model also?
Point in time recovery is the concept that a particular set of data can be restored to an exact point in time, rather than just to the time of the last backup file.

In this case with SQL Server, log backups are the usual mechanism for accomplishing this to ensure database consistency. 

FULL or BULK recovery modes must be utilised to allow for point in time restore, with the BULK option minimizing the amount of log space needed for certain operations (CREATE INDEX, SELECT INTO, BULK INSERT...). If any of these mechanisms are used, the ability to restore to a point in time using a log backup is dropped, forcing you to restore to before / after the bulk logged operation, for that individual log backup. For more information on this see SQL Server Recovery Models. The reason for this is that the bulk-logged model utilising minimal-logging will not log the data pages to the log file during bulk-logged operations - it will only log the extents that have been changed. Whether you want to use BULK recovery model or not will depend on your individual circumstances and whether you can afford to drop the point in time restores in favour of potentially faster bulk logged operations.

Other than that, FULL recovery model will support your use case.