Sure.
I guess your x tensor has a shape of length 2.
In torch,  dim = -1 means that the operation has to be performed along last dimension, and I think that is why   torch.cat((x, x, x,) -1) == torch.cat((x, x, x,), 1)
(not strictly because it’s links and something but you got the idea)  in your example.
For better understanding :
x = torch.Tensor([[1, 2, 3]])
x.shape
> torch.Size([1, 3])

torch.cat((x, x, x), 1).shape
> torch.Size([1, 9])

torch.cat((x, x, x), -1).shape
> torch.Size([1, 9])

Hope it makes things clear for you.