Practically there is no much of difference between probation period eligibility vs. after completion of probation period. Excepting that, during PP such employees' performance is keenly watched and assessed periodically, as it's treated as some what on-the-job-training or observation period. Also either side will have the option of separation at short notice say about 'one month'. In many instances, employees who have successfully completed the PP only will be 'confirmed' and may be granted an increase or increment in salary. On the other hand for those whose performance in PP if found to be 'not satisfactory' their PP might be extended further periods and reviewed/monitored. If their performance continued to be not improved such persons may be terminated with due notice.
Apart from this, though they do all regular work, their frequency of leave, permission to go out and other such benefits are very much restricted.