c# How does a method declaration inside a class works?

Question

Im new to C# .net platform. When I was debugging code with breakpoints I found a class (IndexJob belongs to dtsearch namespace) with only method declarations. It was new for me to see a class with method declarations. I know that interface and other abstract classes will do this, but this class is not a abstract class and also i did not found this class inside the solution, but I think it was invoked through some assemblies.

using System;
using System.Collections.Specialized;
using System.Runtime.ExceptionServices;

namespace dtSearch.Engine
{
    public class IndexJob : NetJobBase
    {
        protected CApiIndexJobForNet* indexJob;

        public IndexJob();

        public bool ActionAdd { get; set; }
        ...
        ...


        public void AbortThread();
        protected DateTime ConvertToDateTime(dtsFileDate fileDate);
        ....
        ....
        public static IndexInfo GetIndexInfo(string indexPath);
        public void ExecuteInThread();
    }
}

What I want to get cleared is:

1.) What type of a class is this which can declare methods inside itself
2.) Where will be the definitions of these methods