Before time started there was nothing but there were Three SUPREME beings who where beyond ETERNALS with or without time. Before time started or after the end of time they will be there. Those three were -
BRAHMA THE CREATER
VISHNU THE PRESERVER
SHIVA THE DESTROYER
At begining of time Brahma creates Universe, Vishnu take cares of Universe and at end of time Shiva destroyes the Universe for new begining.
There are four eras divided from start of time to end time:
Satya yug
Treta yug
Dwapar yug
Kali yug
These four eras creates cycle of creation,preservation and destruction.
Between creation and destruction all living beings strive to free from this endless cycle and reach ultimate goal of MOKSHA.