Tessellations are repeating geometric patterns, usually built upon a square or triangle grid, folded from a single sheet of paper without any cuts. The denser the grid, the more details or more repeats of the pattern can be made. Tessellations are typically flat, although some patterns include sections which rise above/below the primary plane.
I've set up a separate Google Photos album that includes adjusted photos of tessellations that are useful as phone backgrounds.
When describing my tessellations, I often indicate the type of grid and its density.
Grids are prefolded onto the paper to allow for easier creation/collapsing of repeating patterns. Grids are either square or equilateral triangles (60°).
Square grids are simple to describe because the paper usually starts off as a square. The square is then divided by halves until the desired grid is created (leading to 16-, 32-, or 64-cell grids) or divided into thirds, and then halves (leading to 24- or 48-cell grids.) On occasion, a rectangular sheet might be used, so the density for both width and height are noted.
Triangle grids (which allow for a mixture of triangle and hexagon patterns) can also be folded onto a square, and are divided vertically either by a doubling of 2s or a doubling of 3s, leading to the same vertical divisions as the square grid. 60° angles are folded to match the density. When I describe a grid as 32-triangle, it means there are 32 triangles stacked vertically on the square sheet.
Triangle grids can also be folded onto a hexagon, which allows for easier sectioning of the grid as it follows the same pattern of halving (or thirds->halves) as square grids do. The density refers to the number of triangles from one edge of the grid to its opposite edge.
There are common twists used in square and triangle/hexagon patterns, which typically describe the final shape as well as the construction method, that I use. You can find a detailed list at twistdatabase.com.
There are also some folds and collapses which don't involve twists, and are typically described by their methods such as a "120° pleat intersection". Most of these names I pulled from Eric Gjerde's Origami Tessellations book.