That purple thang is essentially a 6″ long piece of fabric with one slightly curved tapered end and ¼” marking guide on the other end. There is a slot you can place elastic through so you can thread elastic casings. The tapered end you can use to poke out corners, steady fabric near the needle of your sewing machine, hook or move threads on your sewing machine. A quick YouTube search will show you the different ways to use it.
I purchased mine at the Stitch craft show earlier this year after seeing it previously online. This morning was the first time I have tried it out. I am in the process of making a toy with small legs and tiny toes. This can be a difficult job. Once I turned out my legs I used the purple thang to get into the tiny points of the toes. It worked great. The tip is blunt which means your less likely to push it straight through the fabric which sometimes happens using other methods to push out the points. It really got into the small areas. The curve on it came in handy pushing out the light curve on the back of the leg, again sometimes it is hard to turn curves nicely. I used it as a stuff tool too to get the stuffing into the small areas. I discovered the ¼” tab was also good for pushing larger pieces. Without doubt I will be using this little tool again when pushing out points and stuff items, these are my best toes ever. It really made the job much easier. This isn’t an essential item to have in your sewing kit but if you are able to get hold of one I’m sure you will use it.