Sketches are typically viewed as fast drafts of a certain shape. For example, the following diagrams show a hand-drawn sketch of a square and a sketch of a cube, respectively. The main point of these is to provide a rough idea of an object. In the following sketch, we are communicating the idea of a square, without specifying how big that object is:

Similarly, the following sketch communicates the idea of a cube, without specifying how big the cube is:

SOLIDWORKS sketches are a bit different. In SOLIDWORKS, a sketch is a fully dimensional and exact shape that's mostly given in two dimensions. SOLIDWORKS also has a 3D sketches function that's more commonly used with surface modeling. In this book, we will only use 2D sketching. The following diagram shows a SOLIDWORKS sketch of a square with a side dimension of 50 mm. Note that the sketch is different than the one we looked at previously; it is an exact square and not an approximation of a square:

SOLIDWORKS sketches are the starting points of any 3D model. They are the basic guiding elements for 3D SOLIDWORKS features. For example, if we want to make a cube, we have to start by drawing the preceding square sketch. After that, we can extrude it to generate a cube, as shown in the following diagram. Note our initial sketch at the bottom of the cube:

When we create a 3D shape in SOLIDWORKS, we often start by creating a 2D sketch and then apply a feature to it. Then, we keep iterating those two steps as the 3D shape becomes more complicated. This is why it is very important that we master SOLIDWORKS sketching before anything else.

The preceding diagram also shows the common sequence of a SOLIDWORKS model, starting with a sketch rather than a feature. The sequence then repeats as the model becomes more complex.