You can compare Pocket with Instapaper, ReadItLater and similar sites.
1] strips out all the extraneous cruft from an article, keeping only the text (in a typeface and font size of your choosing) and any included photos/videos;
2] acts as a centralized archive of articles, which can be tagged and favourited at will (so you don't need to bookmark articles in the browser for later reading); and
3] is available across multiple devices (phones, tablets, PCs) for a single account, including offline access.
It's an awesome experience to simply right-click-save interesting articles in your desktop browser during a work break, knowing that you'll be able to read them whenever and however you like, for example on your tablet in bed in the evening.
Give it a try yourself, that's the only sure way to find out.