This is a video of a gastroenterologist performing a colonoscopy.  During this colonoscopy he encounters colon cancer.  You will see an instrument with a loop at the tip.  This is used for lassoing the polypoid (finger-like projections) lesions.  The metallic rope-portion of the tool utilizes electro-cautery to burn the base of the lesion for 2 purposes.  First it acts as a low resistance knife to shear the lesion from its' base.  Next, it cauterizes or coagulates the base so that bleeding is minimized.
More commonly, what I refer to as lassoing is termed the snare technique.   The snare technique is most often used to perform a polypectomy during a colonoscopy. When the snare cautery technique is employed, a wire loop is placed around the desired piece of tissue or polyp and is heated to shave off the lesion. Larger lesions may be removed with a single application of the snare or can be removed with several applications of the snare in pieces frequently described as “piecemeal.” Remnants of the lesion after use of a snare can be cauterized or ablated to completely destroy the intended target, but only one technique should be reported to remove a unique polyp or lesion.
Snare devices may also be used without electrocautery to “decapitate” small polyps. Most often the colonoscopy report will specify that a “snare technique” was used, but don’t let alternative terminology throw you off.  The snare wire loop uses functionality such as “monopolar snare,” “cold snare” or “bipolar snare,” which refer to monopolar, bipolar cautery and no cautery respectively.
Let's talk about cautery:
The term cautery comes from the Latin word cauterizare, to brand with a hot iron.  In medicine not only do we use heat and electrocautery but chemical cautery, whereby a caustic chemical us placed on an area to which we prefer hemostasis (stoppage of bleeding).  The first cautery was used several hundred years ago during amputation whereby a red hot iron was placed on the fresh stump after an amputation to stop bleeding.  Ouch!  Note they didn't have very sophisticated anesthesia, back then other than opium poppies, whiskey and chloroform.
The more common electrocautery is extensively used in the operating room and during minor procedures across the globe. 
Question I hear often:  Why doesn't the patient get electrocuted during cautery?  Some incorrect answers I hear are:  The voltage is too low to cause damage.  The patient is grounded.  We use AC not DC (Alternating vs. direct current).  These answers are false.
The real reason why the patient does not get electrocuted during electrocautery is quite interesting.  The wall socket in the US is about 50-60 Hz.  This frequency is slow enough to allow for nerve re-polarization and continued shock and reload.  The Electrosurgical generator (ESG), more commonly referred to as an electrosurgical unit (ESU) or simply as a generator, powers an electrosurgical system at frequencies over 100,000 Hz or 100 kHz.  These radio-frequencies are way too fast to allow the nerve to depolarize and even know what is going on.  Therefore the body acts as a conduit for this energy and the electrons flow through unimpeded.
Doctors also wonder what the difference is between mono-polar and bipolar electrocautery.  In mono-polar the electricity runs through the patient and back into the ESU via the grounding pad (usually placed on the thigh). 
***NOTE:  I have seen some nasty burns when the pad is not placed correctly, is not dry, or the hair on the leg is not shaved before placement.
Whereas during bipolar electrocautery, the current flows between to probes used in the instrument (ie. tweezer heads).  More precise control of cautery.
For a good primer on colon cancer see my previous post on Colon Cancer.