name file context
where name is the function or macro name, file is the source file in which name is defined, and context is a search pattern that shows the line of code containing name. After the list of tags is created, you can invoke Emacs on any file and type:
M-x visit-tags-table
You will be prompted for the name of the tag table; the default is TAGS. To switch to the source file associated with the name listed in tagsfile, type:
M-x find-tag
You will be prompted for the tag you would like Emacs to search for