What kind of business consider as self employed

What type of business could i register  as self employed 
If i want to make small resturant
Or food truck is it ok with OP self emplyed?

No, I do not think so that the food truck will qualify

Just take the UK tax definition for self employed and you should be close

So any kind of profession where you need a special education/ specific vocational training

lawyer, chartered accountant, doctor, psychologist, dentist in self-employed capacity etc.

Food truck or restaurant is a business so you will be an investor

There is a definition of self employed in the guidelines of the BOI, I think