https://support.apple.com/et-ee/guide/mac-help/mchlp2469/mac
Copied form Apple support above:
Move a window to one side of the screen: Press and hold the Option key while you move the pointer over the green button
in the top-left corner of the window, then choose Move Window to Left Side of Screen or Move Window to Right Side of Screen from the menu that appears. The window fills that half of the screen; the menu bar and Dock remain visible.