You can make words ‘*bold*’, ‘/italic/’, ‘_underlined_’, ‘=verbatim=’ and ‘~code~’, and, if you must, ‘+strike-through+’. Text in the code and verbatim string is not processed for Org specific syntax; it is exported verbatim.
To turn off fontification for marked up text, you can set
org-fontify-emphasized-text to nil. To narrow down the list of
available markup syntax, you can customize org-emphasis-alist.
Sometimes, when marked text also contains the marker character itself, the result may be unsettling. For example,
/One may expect this whole sentence to be italicized, but the following ~user/?variable~ contains =/= character, which effectively stops emphasis there./
You can use zero width space to help Org sorting out the ambiguity. See Escape Character for more details.