One of the features of WhatsApp is that you can search for GIFs and send them directly. However sometimes the GIF repository might not have the GIF you want, which is when you might choose to share a link to a GIF instead. Now on Android it appears that WhatsApp is allowing users to download the GIFs before sending them.
What does this mean? Basically when you insert a link into the chat box, a preview will popup of the website of the link in question. However before today, Android users did not have the option of downloading the GIF (iOS users have had access to downloads a while ago). This in turn would let them keep the GIF and make edits, their own caption, and also save users the time from having to click on the link.
Like we said, the feature appears to be live for Android users and now when you paste the link of the GIF in the chat box, you should be able to see the option to download the GIF. It seems that this feature is only applicable to GIF files as according to Android Police, they tested this out with links to files of other formats and could not get the same download feature. Perhaps WhatsApp will change this in the future, but for now it is limited to GIFs.