Dictionary sources including Merriam-Webster, Oxford, Cambridge, show 'invention' as connected by etymology with Latin 'invenire' (to find (out)): they offer what looks like essential agreement on a core of meaning relevant here: something, typically a process or device, that has been invented, discovered or contrived, something never made before; as well as sometimes giving more special meanings having to do with patents (law). (Not further considered here, of course, are widely different applications of the word 'invention' such as 'fiction' or 'genre of musical composition'.) Relevant dictionary definitions of 'innovation' often derive from the verb 'innovate': make changes in something established, introduce some new change or idea, &c.
It seems there is no generally-accepted and specific agreement about the boundaries of the concept 'innovation'. A recent (2016) survey of 15 'experts' gave rather widely various answers about what they thought of the meaning of 'innovation' -- results that appear to support an idea that the concept 'innovation' has somewhat broad fuzzy boundaries, not necessarily a bad thing if one wishes to have a word of wide application for a general discussion. ('Idea to Value, Community for Creativity and Innovation': at
https://www.ideatovalue.com/inno/nickskillicorn/2016/03/innovation-15-experts-share-innovation-definition/)
In practical usage a distinction between the two appears connected with the way in which the meaning of 'invention' has to some degree been side-tracked by the complicated laws of patents for inventions. Originally, an 'invention' in law was also something new-created and practical and specially useful -- special enough to deserve the grant of exclusive trade privileges for a set period, e.g. 14 years. Over long periods of time, the legal definitions of invention in many countries have effectively become much more complex [US Manual of Patent Examining Procedure, https://www.uspto.gov/web/offices/pac/mpep/ ; Guidelines for Examination in the European Patent Office,
https://www.epo.org/law-practice/legal-texts/guidelines.html .]
Against this background, a significant practical use of the word 'innovation' is to allow discussions about technical progress without the discussions becoming side-tracked into legalistic arguments about what exactly constitutes an invention, whether in law or otherwise. This can be helpful for example in broad-based discussions about technical progress that either have nothing to do with questions of patents, or are not to be limited to that topic.
{Added 14 November:} Besides the views expressed in the 'expert survey' already cited, another (and official) example shows a usage of 'innovation' that is broader than 'invention'. The website of the Office of Innovation Development, part of the US Patent and Trademark Office, refers to "our Innovation Development webpage", which turns out to give information for "inventors and entrepreneurs" that concerns not only inventions but also some quite different matters such as trade marks and protectable designs. (Acknowledgement to Michael E2 for drawing attention to the example).
'Innovation' can thus be a broader and more general word than 'invention'. It remains up to any particular writer either to say, more specifically, what s/he means by 'innovation' in any discussion, or else to leave it accepted that the word is somewhat vague. The same applies to whatever is meant by saying that some innovations are 'sustaining', 'evolutionary', 'revolutionary, or 'disruptive': these are vague words with no generally accepted specific definitions in the context. Articles may be written about the way in which some particular author understands and uses such concepts: and the articles may sometimes imply an assumption that the usage that they employ amounts to a generally-recognized definition -- even where no such general recognition really exists. Specific definitions may begin to be needed in special circumstances -- for example if the status of 'innovation' ever brings with it some tangible benefit. But there we begin to come full circle on the reason why there are two words in this area rather than one.