If you don't like your windows resizing automatically when you move them to the side of the screen, you can disable this.
In Ubuntu 24.04:
Settings > Ubuntu Desktop > Enhanced Tiling > Off
Settings > Multitasking > Active Screen Edges > Off
Ubuntu 18.04 / 20.04 / 22.04 (22.04 can also be toggled in Settings):
Open up a terminal and run this command:
gsettings set org.gnome.mutter edge-tiling 'false'
To re-enable edge snapping, run this command:
gsettings set org.gnome.mutter edge-tiling 'true'
Ubuntu 14.04 / 16.04:
First, make sure the CompizConfig Settings Manager is installed.
sudo apt install compizconfig-settings-manager
Then go to Window Management -> uncheck Grid