Tiny Life's Data Folder

Tiny Life's data folder contains several useful folders and files:

Custom Lots, Custom Households, Custom Maps, and Mods are the folders that you can put custom content, including custom maps, into.
Logs is the folder where the game's log files are stored. When you experience an issue like a crash, the information about it is stored in the most recently modified log file. If you restart the game, a new log file is created, so the one that contains the information about the issue becomes the second most recently modified file, and so on.
Saves is the folder where your save files are located. If you want to share a save file with a friend, or back it up manually, you can do so from there.
Screenshots is the folder where the game's screenshots (captured using F12 by default) are stored.
There are several files that are also stored in the data folder, like the game's options and installation information.

There are several ways of locating this folder, and its location differs based on the operating system you're using.

From Within the Game

You can open the data folder easily from within the game by going to the options menu and opening the rightmost tab ("Custom Content"). The tab contains a button to quickly open the data folder.

From Your Computer

Windows

On Windows, you can simply open a file explorer window and paste the following text into its location field:

%LocalAppData%\Tiny Life

This should automatically cause the explorer to navigate to the appropriate folder.

Linux

On Linux, you have to navigate to your home folder (also known as ~) first. This is usually /home/username. From there, you can navigate to .local/share/Tiny Life.

Since .local is usually a hidden folder, you might have to configure your file explorer to display hidden files as well.

You can also use a command line to navigate to the folder directly using the following command:

cd ~/.local/share/Tiny Life

Mac

On Mac, you have to navigate to your home folder (also known as ~) first. This is usually Macintosh HD/Users/username. From there, you can navigate to .local/share/Tiny Life.

Since .local is usually a hidden folder, you might have to configure your finder to display hidden files by pressing Cmd + Shift + . together.