Perfectly understandable when you have just been diagnosed - especially when you have been given no information! When I was first diagnosed I went home and started giving all the stuff I thought I could no longer eat to my neighbours! After a few months I learned that I could have kept most of the stuff! What you will come to learn too is that nothing is forbidden with diabetes, you just need to keep some of the 'naughtier' stuff for special treats.
If you look in the link I gave, there are some further links to GL diet books - these will give you the best idea of the types of food that are best for keeping your blood sugar under control. Start thinking 'carbohydrate'. Carbs are the things that will raise your blood sugar levels - things like potatoes, bread, rice, pasta etc. You will still be able to eat these things, but may need to keep an eye on portion size and also learn which types will release their glucose into your blood slowly when they are digested. A good example is bread - white bread is the worst, seeded or granary bread is generally much better as the seeds and grains slow the digestion and release of glucose.
As I said beofre, you will learn what food is best for you in time - there are some general principles, but people can react differently to the same things so it can be a very individual thing. We're here should you need any advice.
They can check your type by doing one or two tests. Type 1 is when your pancreas has slowed or stopped production of insulin, which you need to process the energy you get from food. They can check if this is happening by measuring something called C-peptide, which is produced in the same quantities as insulin - if it is low then your insulin production will also be low, suggesting Type 1. Type 1 is also what is known as an autoimmune disease where your own immune system attacks the cells in your pancreas - the test can check if this is happening to you. If you are Type 1, then the treatment will be insulin injections (don't worry, they are tiny needles that go into a layer of fat below the skin, not a vein or anything! Most of the time they are painless!)
Type 2 diabetes is generally due to something called 'insulin resistance' where you are still producing insulin but the body cannot use it properly. Type 2 can be controlled by modifications to diet and exercise, or by taking tablets which help to control the glucose. It is possible for Type 2s to be started on insulin injections, but relatively rare as they tend to be producing their own and just need some help to use it properly!
Hope this helps! 🙂