system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is a tensor?
gpt
A vector is an arrangement of values in one dimension, like this:

    V = [a, b, c, d, e]

etc. 

A matrix is a vector of vectors. For example

    v1 = [ a, b, c ]
    v2 = [ d, e, f ]
    v3 = [ g, h, i ]

          v1,       a, b, c,
    M = [ v2, ] = [ d, e, f, ]
          v3,       g, h, i

You can think of a matrix as a two dimensional arrangement of values.

A tensor is a vector or matrix of matrices. You can think of it as a three or higher dimensional version of a matrix.