Sketch shape is controlled by (by default, they are automatically applied as you sketch) and sketch size is controlled by . You can leave some sketch geometry undimensioned if you want to change its size later.
Although you create most features from sketched shapes ( ), some features are well-defined mechanical operations that do not require sketches, such as chamfers, fillets, shells, and face draft. Sketched features can join, cut, or intersect with another feature.
You combine features to create complex parts. Features are positioned using geometric constraints and dimensions. If you leave some curves on features undimensioned, you can make the feature , so it can change size when you constrain it to fixed geometry in an assembly.
When you create or open a file of the assembly type, you are in the assembly modeling environment. Assembly commands manipulate whole parts and , which combine to form . When you edit a part from an assembly, you activate it and make edits in the part environment, where Sketch and Feature commands are available. When you finish edits, you save the file and double-click the top-level assembly icon in the browser to return to the assembly environment.
By contrast, the Update command regenerates only the geometry that has significant edits held in memory. If the Defer Update option is selected (on Assembly tab of the Application Options dialog box), you can continue working without incorporating edits to geometry until you click Update.