# A small question on notation- $\delta_{ij}$ and $\epsilon_{ijk}$ [duplicate]

I'm just reading through some vector calculus notes and it begins to assume knowledge of the notation $\delta_{ij}$ and $\epsilon_{ijk}$ in reference to tensors, but I am not familiar with this. It uses them as if they are constant and well-defined.

If someone could just explain this I would appreciate it. Thank you.