I'm a non-mathematically inclined amateur whom is presently interested in Hamiltonian paths / Traveling Salesman problems.

I would like to request that someone be kind enough to tell me whether my understanding of the following sentence found in this research paper (http://www.cs.technion.ac.il/~itai/publications/Algorithms/Hamilton-paths.pdf) is correct:

"In contrast, the Hamilton path (and circuit) problem for general grid graphs is shown to be NP-complete"

My understanding:

- A grid graph is this type of graph: http://mathworld.wolfram.com/images/eps-gif/GridGraph_701.gif
- NP-complete means if anyone can solve it, then a non general grid graph can be converted int o a general grid graph and be solved using the same algorithm.
- Traveling Salesman Problem is a Hamiltonian path (circuit)

Additional questions:

- Is the paper credible?
- What does the 'general' in 'general grid graph' mean?