Why does Cura create this turquoise support structure?

[ac2022 0]

I am just using Cura for the first time.

This is what my model looks like in Fusion 360:

 

 

Here is a close-up look:

And this is what Cura creates for me:

 

 

I assume the turquoise area is a support structure.

Why does it do that? 

 

Also, I don't understand why it marks the edges as red.

I assume this means that there is problem.

 

Thank you!

Edited September 17, 2022 by ac2022
Added image

[GregValiant 1,141]

That is called a brim and it has three functions.

1. Help hold smallish parts down so they don't break loose from the bed.
2. Provide additional hold down stiction so corners and long thin sections don't lift off the bed.
3. Get the flow going smoothly through the nozzle so any burps or bubbles are in an area that gets thrown out.

In Cura turn on the Custom button to get the advanced control settings.  There is a "Settings Search" box and to the right of that box is a Setting Visibility button with three lines on it.  Click on it and set the Setting Visibility to "All".

Go down to the Bed Adhesion section.  You can change the brim to "Skirt" or "Raft" or "None".  I generally use a Skirt 3 loops wide and 3mm from the model.  It's enough to get the plastic flowing and doesn't need to be removed from the part.

For models that need a brim (and some absolutely do) you can set the Brim Distance to a small number like 0.1mm.  That will make it easier to break the brim off the print.

Your print has enough surface area on the bed that you should be able to get by with a skirt.

[obewan 37]

To me it looks like your model is sitting above the bed and so cura is generating a support under it.

On the left side of cura there is a option to 'drop model to bed' , make sure that is selected.

 

[GregValiant 1,141]

I missed a question.."Why does it mark the outside in red?"

The color in the preview tells you the type of line.  Red is "Outer Wall", green is "Inner Wall", etc..  If there was an error in the model it would show in the Prepare stage.  It can be stripes (the model is outside the buildplate), polkadots (the model has internal errors), or red.  Red in the Prepare stage can mean "Overhang" that needs support or sometimes it will be an indication of problems on the exterior of the model.  Red "model errors" generally mean that the surface was created inside-out and Cura won't be able to figure it out.  Flipped Normals are generally facing upward where a good surface that would simply require support would be facing the build plate.