When working on images with Illustrator, one of the first things you should know to do is to make the background transparent. Indeed, when working on images with layers, it is important that the background does not interfere with the upper layers.
Step 1. Open Illustrator
Open or create a new image, then go to "File"> "Save for web…"
In the window that opens, you can save your image in different formats: GIF, JPEG, PNG-8 or PNG-24. Choose the format you want except JPEG
Step 2. Save in Portable Network Graphics (PNG) format
You have two options: PNG-8 or PNG-24. The main difference between the two is that PNG-8 understands 256 colors while PNG-24 supports up to 16 million, but it's a format that compresses less. Once your choice is made, check that the Transparency box is checked (normally it is, by default).
You should see the transparency checkerboard below your image, like above
Step 3. You can also choose to save it as.gif" />
As for the.png" />
Step 4. There you go
The background of your.png" />