C # property is of type list, received many list k? Can

I see many online samples talking about Generics List<T>.

I’m just not sure if T is just a way for the narrator to define “any type” or if I can actually use the syntax List<T> to define a property that can receive any type of LIST.

If not, then what is the right way to define a property that can be populated with either List<MyType>, or List<YourType> or List<AnyType> ??

The reason I’m asking is also because on my WebService that property is giving me the following error:
The type or namespace name 'T' could not be found (are you missing a using directive or an assembly reference?)

and off course I already have the using System.Collections.Generic; on top.

SOURCE CODE:

using System.Collections.Generic;
using System.Runtime.Serialization;
using System.ServiceModel;

namespace StackOverflow
{
    [ServiceContract]
    public interface IDbSync
    {
        [OperationContract]
        int UploadTable(SecurityToken token, TableData table);
    }

    [DataContract]
    public class SecurityToken
    {
        string id = "";
        string token = "";

        [DataMember]
        public string ID
        {
            get { return id; }
            set { id = value; }
        }

        [DataMember]
        public string Token
        {
            get { return token; }
            set { token = value; }
        }
    }

    [DataContract]
    public class TableData
    {
        List<T> data;
        string tableName = "";

        [DataMember]
        public string TableName
        {
            get { return tableName; }
            set { tableName = value; }
        }

        [DataMember]
        public List<T> Data
        {
            get { return data; }
            set { data = value; }
        }
    }
}