When you have multiples applications running on Mac then switching between them becomes tedious task, especially if you are not switching using keyboard. Here is the simple way to switch between applications using a simple key combination, this is almost similar to alt + tab on Windows.
Command + Tab and Command + Shift + Tab
I prefer to use the above method, however there are other two ways to switch between applications.
Swiping up with three fingers
By swiping up on trackpad with three fingers you can easily see all the open applications and you can switch to any app just by clicking on it.
Dot at the bottom of application icon in Dock
This one is obvious, you can easily see which applications are open by just seeing a dot beneath their icon in the Dock area. Just clicking on the icon would switch you to that application.