As to why Flickr matters, it's most people's favourite photo archiving and sharing online service, if only because it lets you keep your photos at full resolution and doesn't try and 'adjust' or downsample them for you.
From the Store description for Perfect Flicker:
The best third-party Flickr app designed exclusively for Windows 10 Universal.
Some major features:
- Put your free 1000GB to work - upload all your photos and videos to your Flickr
- Engage with friends, family and explore the Flickr community - there are millions of groups and billions of photos out there to discover.
- Watch mini thumbnail while browse others.
- Sign in your Flickr account and manage your photostream, albums, favorites, groups, contacts...
- Pin profile, albums, groups to startscreen.
- View, share and post comments to a photo.
- View camera info, albums and photo tags.
- Download photo and set background / lockscreen.
- Browse and join group.
- Follow / Unfollow people.
- Upload photos from your camera roll to Flickr automatically.
In use, Perfect Flicker works very well - it's pretty and functional, using the UWP design principles - on the whole (there are some exceptions). And with only a few bugs, panes that you can find yourself in with virtually a blank screen. But 98% there and on the initial release, so well done all round - and did I mention that Perfect Flicker seems to be completely free?
Here's the app in action:
Not shown here, but you'll be wondering about adding photos to Flickr groups - this is something I do almost daily. When viewing one of your own photos, the '...' menu includes a simple 'Add to group' function and you can then add the image to a single group. Repeat for multiple Flickr groups etc. This could be a little more elegant, but remember, this is only version 1(.1)....(!)
And to prove that Perfect Flickr is a true UWP app, here it is installed and running on Windows 10 on a PC desktop: