Difference between IList<T> and IEnumerable<T>?

Before going into the deep let's consider a simple example below

IList<string> strings = new List<string>{"a","b","c"};

IList<object> objects = strings; (invalid No conversion from IList<string> to IList<object>)

Now the question is why it is not allowed and the next question is what is the difference between IList<T> and iEnumerable<T>?

if i will answer this question in simple word , it would not be safe .

Because the methods within IList<T> allows values of type T as input as well as output. What ever way you use IEnumerable<T> ends up with T value as a output, But there are few methods in IList<T> like Add takes T values as an Input.

Let's understand it in more comprehensive way, take one example

IList<string> strings = new List<string>{"a","b","c"};

IList<object> objects = strings;

objects.Add(new object());

string element = objects[3]; (Retrieves it as a string)