Trademarks are important for companies as they are what people easily identify the company with. It could be the logo or the name or any other idiosyncratic element that would make someone instantly recognize the brand and that is why these companies go all the way to trademark to ensure their continuity.
Instagram is a huge brand on its own with several idiosyncratic features like its logo, the user interface and much more and it would make sense for the company to see it fit to protect that.
According to Trademark Ninja, Instagram filed a trademark through their German Lawyers where they wanted the word “gram” as their trademark. This is a screenshot of the actual file
Instagram has been quite specific in what context the word gram should be trademarked since the word is also a metric unit and a name given to people. This is what Instagram has put limitations regarding the name:
Downloadable computer software for modifying and enabling transmission of images, audio-visual and video context; downloadable computer software for viewing and interacting with a feed of images, audio-visual and video content and associated text and data; computer software for social networking.
As you can see, Instagram wants to limit the use of ‘gram’ in the software sense which when granted would not allow people to come up with software that does the above mentioned restrictions to have the word ‘gram’ in it.
In 2013, they had put guidelines in how you should use their brand assets which included the use of “Insta” or “Gram” but that has not worked well so far. With this move, it will give them the legal right to pursue these apps and stop them.