Gastritis is a general term and refers to different conditions that nevertheless have one common element: inflammation of the gastric mucosa.
Often, this inflammation is the result of infection by the same bacterium that causes most gastric ulcers, Helicobacter pylori. Regular use of certain analgesics and excessive alcohol consumption are other factors that may contribute to the onset of this condition.
Gastritis can occur suddenly (acute gastritis) or appear slowly over time (chronic gastritis); in some cases, it can lead to ulcers and be associated with an increased risk of stomach cancer.
For most people, however, gastritis is not serious and improves quickly with treatment.