Simple try/catch not making any use of the exception

I have searched for an answer to my question but not been able to find one. Apologies if the answer is there and I am duplicating!

I keep seeing try/catch code such as.....

try
{
    //Do whatever
}
catch (Exception ex)
{
    MessageBox.Show("Oops, something went wrong!");
}

Which will result in a warning ex is never used.

So my question is... Although ex is never used is there any benefit in the declaration? I was told that maybe it adds detail to the stack trace? Sometimes I see catch(Exception) which stops the warning but what benefits does this bring, if any? If I was to write this and not use the exception in any way I wouldn't declare ex...

try
{
    //Do whatever
}
catch
{
    MessageBox.Show("Oops, something went wrong!");
}

Not a big problem but it would be good to know for sure!

Thanks

Fred