What are the different kinds of GI cancers?

Many. Oral cancer/pharyngeal/esophageal/stomach/pancreatic/liver/colon/rectal/endocrine cancers (usually related to the pancreas). Histologically there are squamous cell cancers, adenocarcinomas, stomal cancers, lymphomas etc. Etc.
Starts with the. Esophagus, then stomach, bile ducts from liver, through and from pancreas, small bowel (dudenum, jejunum, ileum), appendix, colon, rectum and anus. Gall bladder, liver and exocrine and endocrine pancreastic tumors.