Opening Phase
The opening phase is a battle of memorization. This is because the only position that happen in every game is only the first turn. Even though there are practically infinite number of possibilities in a game of chess, there are only so many 'good' opening that brings advantage to a player over their opponent.
While learning opening theory sounds scary for a beginner, it doesn't have to be. The general rule of thumb in opening phase is to develop your pieces or put your pieces in a more active square and get some sort of control of the middle board with the pawns and said pieces. You can try to experiment with some of your own opening combination before trying to look for opening theories. For beginners, some of the suggested openings are the London System for white and the Scandinavian Defense.