In the following thread I'm talking a bit about how tags are saved in the SDLTM, maybe this can help you:

Wondering if it's just the start and end tag element as explained in my link.

In the following thread I'm talking a bit about how tags are saved in the SDLTM, maybe this can help you:

Wondering if it's just the start and end tag element as explained in my link.

Not really, this concerns an SDLXLIFF file.

If you look at this unit, the <x id="76"> tag resolves to <uicontrol varref="PP_Desktop" id="GUID-B0F3D486-0E6F-4B50-937D-49912563D292">Desktop</uicontrol>

If you look in the <tag-defs xmlns="sdl.com/.../1.0"> element, there are two entries with <tag id="76">

and

How can we know to which tag entry the x id refers to?

Although the tag has the same id value those are different tags. The first one is an inline placeholder tag that can represent textual content or invisible location references. The second tag represent a structure tag that represent the document structure. Since you are looking after inline content from your segment means you need to look after the placeholder tag. A placeholder tag is starting with ph and is inside a tag element.