When a pet vomits, the stuff they brings up comes from their stomach and sometimes the first part of their small intestine. If there's yellow or orange-colored bile or digestive fluid, you know your pet is vomiting. Most of the vomit contains bile.
On the other hand, reappears from either the esophagus or the pharynx (the back of the throat), which is why sometimes it's shaped like a tube. It's typically a mixture of food, saliva, and sometimes mucus (a slimy substance) – but not bile.
(Something they cough or spit out (phlegm) from the throat or lungs), a third variety of this subject. Many pet owners can confuse this event with vomiting. When an animal coughs -- a few times or several times -- and then produces a blob of mucus (a slimy substance), she is expectorating, which is very different from regurgitating or vomiting. The key with expectoration is that there's always a cough involved.
If any of the symptoms happen after few minutes or even few hours after feeding. It could be regurgitating. It happen on pets when they switch to new diet, when they eat too quick, play too much after food or even so do nothing but cause by gas. It happen more often of regurgitating on a cat.
It is not a sign to worry if it happen occasionally, but only to worry when it happen on daily basis. Normally they will get back to normal after they adapted to their new diet.