This extract, from Healthline.com, explains how carbohydrates are digested by the body. (There are three types of carbs - starches, or complex carbs, sugars or simple carbs and fibre).
All the food you eat goes through your digestive system so it can be broken down and used by the body. Carbohydrates take a journey starting with the intake at the mouth and ending with elimination from your colon. There’s a lot that happens between the point of entry and exit.
1. The mouth
You begin to digest carbohydrates the minute the food hits your mouth. The saliva secreted from your salivary glands moistens food as it’s chewed.
Saliva releases an enzyme called amylase, which breaks down the sugars in the carbohydrates you’re eating.
2. The stomach
From there, you swallow the food now that’s it’s chewed into smaller pieces. The carbohydrates travel through your esophagus to your stomach. At this stage, the food is referred to as chyme.
You stomach makes acid to kill bacteria in the chyme before it makes its next step in the digestion journey.
3. The small intestine, pancreas, and liver
The chyme then goes from the stomach into the first part of the small intestine, called the duodenum. This causes the pancreas to release pancreatic amylase. This enzyme breaks down the chyme into dextrin and maltose.
From there, the wall of the small intestine begins to make lactase, sucrose, and maltase. These enzymes break down the sugars even further into monosaccharides or single sugars.
These sugars are the ones that are finally absorbed into the small intestine. Once they’re absorbed, they’re processed even more by the liver and stored as glycogen. Other glucose is moved through the body by the bloodstream.
The hormone insulin is released from the pancreas and allows the glucose to be used as energy.
4. Colon
Anything that’s left over after these digestive processes goes to the colon. It’s then broken down by intestinal bacteria. Fiber is contained in many carbohydrates and cannot be digested by the body. It reaches the colon and is then eliminated with your stools.
Note that even complex carbs are dealt with like this, and - along with sugars and simple carbs - turned by the body into sugars, and ultimately glucose/glycogen.
TL:DR carbs = sugar/sugar = carbs.