There are all kinds of things to collect in Pandanda; mushrooms, potatoes, onions, litter, gems, treasure chests, and keys to open them.
Once you’re close enough you should notice that your cursor changes to the “Paw” icon when your mouse is over the object. This indicates that you can pick it up.
Simply click on the object and it is yours!
Everything you collect is added to your backpack. You can click the backpack icon in the lower right corner of your screen to see all of your stuff.