Yes, it's true - you can edit multiple products at once! It's a feature that will certainly will make your life easier. Below I'll present few use cases which you can perform during bulk actions.
If you want to edit few products then you go to Product Catalog, and check products that you'd like to edit. Click on the green button that says "Actions" and choose the option "Edit products". Once you click that option, you'll see another window that will enable to edit those products:
On the left side you can see all the attributes that appear in the product template that is assigned to the edited products. For example, you've got a product that uses a template called "Casual Shirts" and another product that uses a template "Semi-casual Shirts". Each template has a set of attributes, and this list will present the attributes that only appear in both templates. To clarify more, let's say that "Casual Shirts" template has three attributes: Color, Size, Sleve Length and "Semi-casual Shirts" has four attributes: Color, Size, Collar Type, Material. In that case, a user will be able to bulk edit only those attributes: Color, Size.
From that list you can drag'n'drop the chosen attributes to the space on the right. If you don't want to edit the attribute that you placed on the right side you can delete it by clicking on the closing icon. You can also change its order by clicking the two arrows on left side and moving it up and down.
Once you're done with editing, you simply click button "Save changes". If you leave one attribute unchanged, then the system will automatically try to update it with an empty value.
So make sure all the attributes that you've chosen are edited, and then click "Save changes" you'll see once again the pop-up where you're asked to confirm your action, and that's it. The bulk editing will continue to perform in the background so you're free to go back to your work.
Once it's done you'll be notified about it in the Action Center.