It is an effect loved by many guitarists!

An overdrive pedal is a type of effect used by guitarists to add a distorted, crunchy, or overdriven tone to their guitar sound.

When a tube amp is given more signal that it can cleanly produce, it results in a warm, saturated, and compressed tone that many guitarists came to enjoy. The problem being that you had to have your amp cranked to get this tone! An OD pedal's job is to recreate this sound at lower volumes while also giving you more control over how to sculpt it.

When a guitarist engages an overdrive pedal, it increases the gain of the guitar signal, and adds a level of distortion. Most overdrive pedals have controls to adjust the amount of gain (often labeled as "drive" or "gain") and the overall output volume. Some overdrive pedals also feature tone controls to shape the frequency response of the sound.

Guitarists use overdrive in various ways, depending on their musical style and preferences. Overdrive can be used to add a subtle amount of grit and sustain to their clean tone, while others crank up the gain to create a heavily distorted sound for solos or rhythm parts.

Overall, the overdrive pedal is a versatile tool that guitarists use to achieve a range of expressive tones!