Can anyone tell me please why I should buy blocks AND stacks together. What is blocks giving that I cannot do with stacks
There is no reason at all to buy both together. Stacks is IT. Blocks came before Stacks existed. It was interesting and useful In those early years, but Stacks has supplanted it.
Blocks was akin to desktop publishing on the web. But that metaphor no longer (perhaps never) worked really well on websites. Stacks is fluid, adaptable, and comes with many “stacklets” that allow you to do special things.
Three things: 1.) get Stacks, 2.) get Stacks, 3.) get Stacks. Stacks (upper case) uses “stacks” (lower case) add ons. Stacks uses “stacks” are made by add-on developers and there are tons of them. Read through the forum here to get an idea of what some stacks may do. Some stacks are very complex (do complex things) while some do incredibly simple things. A stack may add a scrolling banner at the top of a page, adjust a layout for mobile, while another may simply house “notes” that only you see when editing.
A key part of Stacks is “Partials” - Learn all about partials before you get too heavily into stacks. Use partials when it makes sense to do so. It will save you from making the same change on all your pages. Change a partial and it changes on all pages where that partial is used.