This is a very simple app that will take a shared file (e.g. an image, Word document, e-mail attachment etc) from another app, save it to the "Download" folder in your phone's storage and then open it. There is also the option to send via Bluetooth instead.
This app does not have a shortcut icon - you access it from the share menu in your favourite app, from where you want to save and open a file. Two options are shown: "Save and Open" or "Save and Bluetooth".
This app is particularly useful where the share button doesn't list all the apps capable of opening the file. It's also useful if you want to edit or send a file, and want to avoid the effort of having to save it first, then go and find it and open/send it.
The shared file is saved in your Download folder. It is probably called /sdcard/Download or /storage/sdcard0/Download or similar. Where an identical file already exists, a numerical suffix will be added to the file being saved (e.g. "test-1.pdf" rather than "test.pdf").
You will need to grant write permission to the app to save the file.