The typewriter is distinct and often intermediate writing device standing between the markedly free-form though also variable handwriting and the much more standardised, though fairly developed, capabilities of typeset documents.
Unlike handwriting, typewriting uniform (both in type and spacing), and markedly faster.
Unlike printing, typewriting is limited (generally a single typeface, no variability in face, size, or styling (e.g., roman, bold, italic), and requires further guidance to define specifically what result is desired where a typewritten work is not a document's final form.
It's worth noting that print itself differs from handwriting: when we write letters, forms and sizes vary, different writers often differ markedly in their own scripts, trained copyists may achieve a high level of standardisation, but that itself requires significant training and is achievable only by a limited number of artisans,[1] and letterforms themselves are not discrete but individually instanced each time they are created. With the advent of moveable-type printing,[2] letterforms became fixed, and with digital typesetting and computer fonts, each discrete shape or language-specific forms, say, the Roman A, Greek Α (alpha), and Cyrillic А (Azǔ/Азъ), are represented by distinct code points, but are nearly or entirely indistinguishable when rendered on-screen or in print. Further, over the history of both handwriting and typesetting, conventions have emerged for the textual representation of language, including spacing of words (versus scripto continuo), punctuation, paragraphs, page numbering, division of books into chapters, sections, parts, subsections, etc., of lists, tables, indices, (foot|end|side)notes, (parenthesis), drop-caps, figure captions, cataloguing, etc., etc. All of those were inventions and conventions not inherent to language, writing, printing, document preparation, or archival and retrieval themselves. There's still considerable variation between different print language representations, e.g., many texts lack equivalents of italic, bold, or even upper/lower case letterform distinctions.
Typewriting itself occupies an interesting space, being a primary endpoint for some types of documents (correspondence, forms, and the like) and an intermediate form for others, most notably published articles and books. Given that typewriting has both capabilities and limitations which aren't present in typeset documents (whether moveable type or digital), it's not possible to draw a distinct correspondence between what a typewriter outputs and how that might be represented in a derived document. Yes, typewriters can generate underlines, but that might be represented in typeset print as italic, bold, underline, or something else entirely. In practice, editors proofing marks were inserted (as handwritten notations) on a typed manuscript to indicate the preferred presentation, generally following the author's intent and/or the publisher's own house style conventions. See: https://en.wikipedia.org/wiki/List_of_proofreader%27s_marks>.
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Notes:
1. An anecdote which sticks with me: among the 1001 Arabian Nights stories is one in which a character makes specific references to the not only his literacy and scribal capabilities, but the types of scripts he could produce. That is, this was a specific and valued skill of that age worth noting, even in a general-audience work.
2. As distinguished from earlier monoblock printing in which a whole work was engraved on a wood block or metal plate, typified by early Pamphilus, seu de Amore from which we have the word pamphlet, see: https://www.etymonline.com/word/pamphlet>. Such monoblock prints were more like a photocopied handwritten letter, in which variations in individual letterforms are replicated, than they are standardised print obtained from moveable type or, more recently and familiarly, computer-based digital typesetting or Web documents, in which fonts are standardised and each given character is identical to all others matching that style.