VTags is project that lets [x]emacs use the same (sorted) TagsFiles that Vim uses. It does not read the file into a buffer but rather does a binary search of the file on disk. Thus it is fast and uses less RAM than
‘etags’ (see EmacsTags). It is quite usable, but does not have all of the features available with either of the current etags.el implementations. Frankly, some of the features of etags.el are pretty obscure and/or don’t make sense in the context of vim-style tags files. See https://savannah.gnu.org/projects/vtags.
By using Vim TagsFiles, VTags provides the following Vim feature: When a tag has multiple entries in the tag file, Vim makes a list of the files the tag appears in – then you can choose one by selecting a number. You can thus search trees where there are multiple files that implement the same functions for porting reasons.
These libraries also let you choose among multiple tags for the same name: