Shapes

Flat means not round, and not bumpy, just even and level, like a flat table or a flat road.

The landscape in the picture is very flat.

A form is the shape of something, or a framework made around the edge of an empty space that then is filled to make a shape. The picture is of some forms about to be filled with concrete to make the floor of a building.

Globules are small lumps of something that are almost spherical.

A helix is a curve in three dimensions. The thread of a screw is a helix, and wire coiled around a rod makes a helix. A spiral staircase is a helix. Some plants, like in the picture, naturally grow into helixes.
The word "coil" is sometimes used to mean a helix and sometimes used to mean a spiral, or sometimes used to mean the act of wrapping something around something else to make a helix or spiral.

A hexagon is a shape with six sides. The hexagon in the picture is a wooden box.

A line is something thin that only goes in one direction (or one dimension), and has no corners. The sides of other shapes are drawn with lines. The picture is of lines painted on the floor of a railway station.

A nugget is an uneven shaped lump of something. The two things that most commonly come in nugget form are gold nuggets and fried chicken nuggets.

An octagon is a shape with eight sides. The stop sign in the picture is an octagon, and it is mostly red.

An oval is like a circle that is not perfectly round. Ovals have one long, curved edge but are not the same size in all directions. Their width and height are different.

The mirror in the picture is oval shaped.

A parallelogram is a shape with four sides. A parallelogram looks like a rectangle that has been pushed sideways. Both pairs of opposite sides are parallel and the same length. The windows in the picture, viewed from this angle, look like a parallelogram. In fact, each of the windows is a little parallelogram by itself.