How to use InjectionFactory in C# Unity

I am new developer using C# and I am working on a project which uses C# Unity for Dependency Injection. So the current code is like this

ISomeInterface var = new SomeConcreteType(param);
ContainerFactory.Container.RegisterInstance<ISomeInterface>(var);

Now, I want to have var1 and var2 which are of type ISomeInterface. I read online the InjectionFactory can help in this case but I am not able to figure out how that works.

Can someone explain to me how InjectionFactory works?

Like if I do this

 ContainerFactory.Container.RegisterType<ISomeInterface>(
            new InjectionFactory(
                container => new SomeConcreteType(param1)));

ContainerFactory.Container.RegisterType<ISomeInterface>(
            new InjectionFactory(
                container => new SomeConcreteType(param2)));

How does then the Unity decide which one of the SomeConcreteType to inject.