RSS : Some people say RSS stands for "Rich Site Summary" and some people say it stands for "Really Simple Syndication". Let's face it, despite of this complicated situation, RSS is simply a kind of SUMMARY of your latest content and it is distributed to your RSS subscribers automatically. (Cambridge dictionary says for Syndicated: (of articles and photographs) sold to several different newspapers and magazines for publishing)
XML : It stands for eXtensible Markup Language. It is a kind of computer language which is used to label text and its pieces. It is extensible because it can include as many subjects as needed. Markup means to put labels on something, in other words to mark something. (up is used for emphasis or to say the completeness or completion of an action.) XML was inspired by HTML. HTML is a computer language which is used to write webpages with many capabilities and decoration. They liked the text labeling in HTML so much that they wanted to use it for whatever else that could be labeled and this new language was called XML. In RSS we are labeling things with XML-language, so that's why these words appear together.
HTML : It stands for HyperText Markup Language. Hyper- means above, beyond. Hypertext means above text, beyond text. It is any computer text which you can browse from page to page by clicking links (since 1965). Markup is to put labels on something. HTML means a computer language which is used to put labels that gives various capabilities and decoration (this was the markup part) on a text which you can browse around from page to page by clicking links (this was the hypertext part.) A web page is what you see in front of you and it is produced by an above text which has labels around the actual contents describing what the content is and where and how it should look on the page.
Blog : It is short for weblog. That is not the weblog where a website's activities like visits, visitors etc. are recorded. It is a webpage in a site where you write in the style of a diary. You can write everyday, everyweek. every month or whenever you want. Everything is on cronological order and there is a feeling of a diary.