Google Keep is apparently codenamed "Memento", and there are a few trails leading back to it. For example, the URL https://drive.google.com/keep/
Interestingly, there is a link found for it in a screenshot for Instant Preview in the Android browser from way back in July of 2012. It looks as though the "Add to Google Keep" link will save website snippets from Search directly to the Google Keep app, which will be part of Google Drive.
So, Google Keep could just be a Pocket/Instagram type of app, or we think it may be something of a rebranding of Google Tasks, and could be a more comprehensive read later/notebook app, similar to Evernote. Whatever it is, it seems like it has been in the works for a while, so it's unclear if we should expect this to really show up, or if the project may have already been put aside.
source: Android Police