launched Drive, it started out by giving users 5GB of free space, and that was kept separate from the storage you would get as a user of Google Photos (aka Picasa), which had 1GB of free storage. Now, Google is changing that policy to have the 5GB be shared storage between Drive and Photos.When Google
If you're someone who uses Photos a lot, but not drive, this will be a good change, because you'll suddenly have 4GB more free space. If you only use Drive, you won't notice a change. And, if you use both, you may see yourself heading towards the need to buy a storage upgrade from Google, which of course also had a big jump in pricing when Drive was launched (20GB used to be $5 per year, now 25GB is $5 per month).
However, one big note is that if you buy a storage upgrade, the 5GB shared storage for Drive and Photos will now be counted as part of the total, not as an addition to the total. This means, if you upgrade to 25GB of storage, you'll end up with 25GB of storage instead of 31GB (25+5+1) that you would have had before.
source: Google Blog