The beginning phase is divided in three steps:
Untap step
Upkeep step
Draw step
In this step you untapp all your permanent cards, that migh for example be lands or creatures (but is not limitted to that). In the first round, there is nothing to untap.
Some cards might require that phase, its written in the text if that is so. Players can cast instants and activate abilities.
The player draws a card from the library (on the first turn, the first player - doesn't. Players can cast instants and activate abilities.