Google - Today my tablet started popping up adverts all the time..not just YouTube but ALL THE?

There is a site google.com where you can enter a word or sentence and get links to thousands of sites that seem to have something on that subject. That has no relation to this site. There is no reason to preface your question with "Google".

Every program you use has a tools menu. If you use tools a lot it will be a toolbar across the top of the screen. If you rarely use tools it might be hidden. In Windows you can click "Start" and select "Control Panel" and that gives you a menu of menus to control everything the computer does. You can right click anything and most of the time get a menu for that specific item. For example if you right click the desktop you have the option to rotate the monitor image in some graphic cards. That allows you to have an image that is high instead of wide, by turning your monitor. You don't need to memorize all these things, just be aware that they are in there. Then you can claim to know how to operate a computer at the beginner level.

What you are talking about is a browser function, so go find the tools menu for your browser, usually in the top right corner of the screen. In Firefox it is called "Options" and you are looking for "Addons". In Chrome it is called "Settings" and you are looking for "Extensions". Search for "ad block". There are several. Try one. Try another.