You may start typing, thinking you are in insert mode, but find that the characters are interpreted as commands because you are actually in normal mode. To help avoid that problem, you can specify that the cursor color and blink rate change when entering insert mode. Using gvim with the defaults, the cursor shape is a block when in n-v-c modes (normal mode, or visual selection mode, or command mode while entering a colon command), and the shape changes to a vertical bar when in i (insert) mode. The color and blink rates do not change.