I don’t do Facebook but the examples You gave are typically used in HTML code to go to a page and scroll to the location where the hashtag is… e.g. a div with the ID of “#liftkeith” will be scrolled to the top of the browser window (assuming there is enough of the page below the hash tag to allow this scroll-to-top action, otherwise it scrolls up as far as it can).
You can also use the hash tag to scroll up/down the current web page to the location of the element ID (aka “named anchor”).
You can also use the hashtag as a “dummy” anchor - i.e. it follows no links, often used in menus.